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CA Chassis Safety Guidelines
HIGH VOLTAGE AND X-RADIATION PROTECTION
A potential source of x-rays is the picture tube, if the high
voltage (HV) is out of specification. When the HV is operating
properly, there is no x-radiation. For the CA chassis family,
the HV has no adjustments. A HV shutdown circuit is used to
prevent excessive HV and x-ray emissions.
SAFETY CIRCUIT TEST PROCEDURE
Equipment required:
a) Video Generator.
b) HV DC meter (0 to 40 KV, high Z).
c) External variable power supply (0V to 200 VDC @ 5Amps
minimum).
THEORY OF OPERATION (SHUTDOWN CIRCUIT)
This circuit basically monitors the sweep pulse voltage derived from the sweep transformer TX3204 pins 5 & 6. This
voltage is rectified, and applied to a 12V zener diode ZDX3004.
When the HV reaches its maximum allowed ,value (see drawing) the zener diode conducts, the voltage on pin 29 of the
video processor (ICX2200) increases until it reaches the threshold voltage of 3.5 VDC, and shuts down the TV. If the shutdown circuit has operated, the microcontroller will prevent
the TV from being turned on again, without first having to
unplug the AC cord to reset the microcontroller.
d) 1 Giga ohm, 5%, 2W film resistor.
Before turning the TV on, connect the HV meter’s negative
probe (-) to ground (DAG ground recommended) and the positive probe (+) in the anode of the CRT. Connect a 1 Giga Ohm
resistor in parallel with the HV meter. Then connect the external power supply’s negative output (-) to chassis ground, that
is, the negative lead of B+ filter capacitor, CX3420. Turn on
the TV. Apply a video signal or tune the TV to a raster pattern.
Adjust the G2 potentiometer for minimum, and set the brightness and contrast levels to minimum. Now adjust the output
voltage of the external power supply to 124 VDC for CA25V/
27V or 130 VDC for CA32V/36V. Then start increasing the
voltage on the external power supply until the TV shuts down,
and read the HV on the meter just before the voltage starts
dropping.
TIP: Make a momentary short between the OUTPUT and GND
of the IC6002 (RESET CIRCUIT) this will reset the microcontroller
IC6000. Apply signal through the video generator or tune the
TV color receiver to crosshatch pattern. Connect an accurate
HV meter between the picture tube anode and chassis ground.
Access Video Menu and adjust Brightness and Contrast controls for minimum screen luminance. Wait until, the Video
Menu or display disappear. Read HV meter.
7'6))2
7->)
Note: The external power supply may require a diode for
blocking voltage from the chassis power supply to
the external power supply. The diode should be
connected between the positive output of the external
power and B+ of the chassis. The cathode should be
facing the B+ of the chassis. The recommended diode
is Part No. 103-00339-04A (400 V of VRRM @ 3
Amps of average rectified forward current).
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,:231 ,:1%<
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CA-ii
Preface
This manual has been designed as a supplement to the CM-151 CA/CB training manual (923-3351TRM).
It provides circuit descriptions as well as troubleshooting flowcharts for both CA and CB chassis. Each
description includes schematic diagrams of the particular section(s) being discussed. These inclusions
represent a change from some recent training manuals. Moreover, this manual is divided into two distinct
sections, respectively, for CA and CB chassis. Such an arrangement should prevent confusion between the
two.
Many servicers prefer to use their training manuals in conjunction with the corresponding service manuals.
As such, the schematics contained in this training supplement were drawn to be fairly generic. However, as
a concession to those who desire a quick reference, tables that include part numbers of major components
have been supplied in each applicable circuit description. Note that these part numbers should only be
applied to those sets which fall under component level repair warranty. (32” and 36” sets have a module
replacement warranty.) Hence, when a table refers to “all models”, it can only apply with certainty to all
component level repairable modules. Likewise, in the troubleshooting section, flowcharts will often instruct
the repair technician to replace a certain component under a particular situation. Again, such instruction
concerns component level repair sets. Still, the flowcharts provide useful information for diagnosing a
problem on component level warranty modules and replacement warranty modules alike.
Frequently, the tables refer the reader to the service manual for particular models associated with given
parts, particularly with regard to the CA chassis. This is because at the time this manual was produced,
there were 81 variants of the CA chassis in the field. In any case, parts referencing is really beyond the
scope of a training manual. Furthermore, it is a good idea when looking up part numbers to refer to up-todate service information. Generally speaking, training in circuit theory and operation does not change when
part numbers do.
Finally, be sure to take special note of the safety information supplied in this manual. General safety information is provided for both chassis on the reverse side of the front cover. High voltage protection instruction for the CA chassis is located on the page following the general safety page and for the CB chassis at the
start of the second section of this manual.
CA-iii
Table of Contents
Section 1
General Safety Guidelines
CA Chassis Safety Guidelines
Preface
This Table of Contents
CA Circuit Descriptions
Power Supply
Microprocessor Control
IF Receiver
Video Processing
Deflection Control
Audio Development
CA Troubleshooting
Section 2
CB Chassis Safety Guidelines
CB Circuit Descriptions
Power Supply
Microprocessor Control
IF Receiver
A/V Switching
Video Processing
Deflection Control
Audio Development
CB Troubleshooting
................................................................................... CA-i
................................................................................... CA-ii
................................................................................... CA-iii
................................................................................... CA-iv
................................................................................... CA-1
................................................................................... CA-5
................................................................................... CA-9
................................................................................... CA-11
................................................................................... CA-17
................................................................................... CA-22
................................................................................... CA-27
................................................................................... CB-i
................................................................................... CB-1
................................................................................... CB-5
................................................................................... CB-9
................................................................................... CB-12
................................................................................... CB-16
................................................................................... CB-22
................................................................................... CB-27
................................................................................... CB-30
CA-iv
Power Supply
Introduction
The CA chassis is a cold ground chassis deriving its power from a switch-mode, flyback type, power
supply. It features indirect B+ regulation, over-current protection (OCP), software controlled degaussing,
necessities for Energy Star compliance, and provision for future universal power input (85VAC - 265VAC).
The switch-mode power supply, or SMPS, converts AC line power to the various DC voltages required by
the receiver. Note that there is no switch to activate or deactivate the SMPS. It operates as soon as AC
line power is present. Input power demands can reach a maximum of 130 watts on 25 and 27 inch sets and
145 and 150 watts on 32 and 36 inch sets respectively.
Switch-Mode Power Supply Primary Side
The receiver is protected from AC line surges by FX3401, a 4A, 250V fast-blow fuse. The AC operating
range is between 90Vrms and 135Vrms. AC is first filtered by LX3401 and CX3402. It is then rectified
using a diode bridge (package DX3400 on 32"/36", discrete components DX3401 through 3404 on 25"/
27"). CX3407 smoothes out the resulting DC voltage. It is from this voltage (called VDC or raw B+) that
the heart of the SMPS, the Switch-Mode Regulator, is run. Raw B+ can run anywhere from +127VDC to
+191VDC.
To Degaussing
Circuit
B+ VDC
FX3401
CX3404
LX3401
3R8
DX3402
DX3401
C3403
DX3400
EX3401
CX3401
CX3402
DX3403
DX3404
RX3401
CX3405
CX3406
CX3407
RX3400
CX3400
<<Figure CA-1>>
Primary components of the Switch-Mode Regulator circuit include the switching transistor, QX3401; the
regulator IC, ICX3400; and the chopper transformer, TX3401. The actual chopper used will depend on
the size of the set. This transformer isolates the rectifier and regulator sections, which use hot ground, from
the rest of the CA chassis, which uses cold ground.
When line power is introduced to the set, raw B+ is supplied to pin 18 of the chopper (switch-mode
transformer). At the same time a small amount of raw B+ is drawn through RX3404 into pin 2 of
ICX3400. This voltage triggers the switching of a transistor internal to the regulator IC. Once this happens,
current begins to alternate between flow and rest in the raw B+ winding (pins 18 and 11) of the switchmode transformer. Alternation will occur at a frequency of approximately 25 KHz when the set is in standby, and near 50KHz when the set is powered up. Because of the transformer action, base drive to pin 2 of
ICX3400 is from this time forward maintained by another winding on the chopper (pins 13 and 15) through
CX3416.
CA-1
CA CIRCUIT DESCRIPTIONS
CX3415
RX3405
B+ VDC
CX3408
B+ VDC
RX3410
PROV
C3414
PROV
RX3411
PROV
DX3409
PROV
CX3409
CX3411
RX3404
RX3407
ICX3400
RX3408
LX3410
DX3406
5
4
3
2
1
B+ VDC
QX3401
RX3406
DX3407
TX3401
CX3416
CX3410
18
8
11
To
+18 VSB
7
13
RX3403
CX3413
CX3412
15
DX3408
RX3409
16
5
1
To
Regulated
B+
4
C3418
<<Figure CA-2>>
Another winding from the chopper (pins 13 and 16) provides feedback to the regulation loop in ICX3400.
The AC from this winding is half-wave rectified by DX3408 to supply a negative voltage to pin 1 of the
regulator IC. ICX3400 is designed in such a way that it will adjust both its oscillating frequency and duty
cycle to maintain -41 volts DC on pin 1. Thus as changing power demands are reflected in the chopper
transformer, feedback to ICX3400 triggers a corresponding change in the regulated supply.
ICX3400
223-00028
5
R-Div1
R-Div2
4
Q-Switching
Q-Limiter
3
2
R-AntiSat
Q-Reg
1
R-Bias
R-Shunt
DZReg
<<Figure CA-3>>
QX3401 serves as the Over-Current Protection (OCP) switch. If the current sensing resistor, RX3403,
passes too much current to pin 4 of ICX3400 (the emitter of the internal switching transistor), the resulting
CA-2
Power Supply
voltage at the base of QX3401 will switch that transistor on, shunting the regulator IC’s base drive to
ground. Such an action kills the regulator’s oscillation, thereby eliminating power generation.
Several capacitors, CX3408, CX3409, CX3410, and CX3412, are used in the SMPS to reduce EMI
(electro-magnetic interference). Additionally, RX3405 and CX3415 serve as a snubber circuit, to reduce
peak voltage on the collector (pin 3) of ICX3400’s switching transistor.
Switch-Mode Power Supply Secondary Side
The two windings on the secondary side of the chopper transformer generate the regulated B+ (or simply
B+) which, depending on the size of the television, will be either +124 volts DC or +130 volts DC, and the
+18 volts DC. Both are present when AC line voltage is supplied to the SMPS. Hence these voltages may
be considered Stand-By (SB). The B+ supplies necessary power to the horizontal sweep and the horizontal output sections. It is filtered and rectified using LX3403, C3419, and D3410, and it can be measured
across CX3420. Note that the B+ line does not have a fuse. The OCP circuit mentioned above serves to
shutdown the power supply if too much current is drawn through the regulated B+ circuit.
L3407
+5V
TUNER
+18 VSB
TX3401
FX3402
DX3411
LX3404
Q3406
PROV
+5 VSB
W3402
ICX3402
8
C3421
IN
R3423
7
1
3
OUT
2
R3427
5
C3419
R3422M
C3426
B+
PROV
1
W3401
4
LX3403
D3410
+18V
AUDIO
CX3424
CX3420
R3424
PROV
C3425
Q3405
PROV
D3414
PROV
R3425M
PROV
R3412M
R3426M
PROV
R3414
Q3404
Q3402
R3418
+18
VSW
+9 VSW
L3405
ICX3401
OUT
3
1
IN
RX3417
+15 VSW
Power Control
Pulse from
Pin 32, IC6000
RX3428
2
C3429
C3428
PROV
CX3430
ZDX3401
C3460
<<Figure CA-4>>
On the other hand, the +18 volts DC (or +18 VSB) is fused by FX3402. Rectification and filtering of the
+18 VSB is accomplished by an arrangement similar to that of the B+. The resulting +18 volts DC may be
measured across CX3424. This voltage is further broken down to provide power to various circuits
described below.
CA-3
CA CIRCUIT DESCRIPTIONS
ICX3402 regulates from the +18 VSB to provide +5 VSB. The +5 VSB powers the microprocessor,
IC6000, and the tuner, TU6000. Additionally, part of the power from the +18 VSB supplies +18 volts to
the audio circuitry (+18 AUD). The remainder of the +18VSB power is used when the set is powered up.
This powered up voltage is typically referred to as a switched voltage (VSW). The +18 VSW powers the
horizontal drive amplifier. That same +18 VSW is also regulated through ICX3401 to produce a +9 VSW.
This +9 volts powers the video signal processor, ICX2200, and, in stereo sets, IC1400. Finally, a +15
VSW is generated from the +18 VSW using RX3428, ZDX3401, and C3460. The +15 volt supply
powers the ABL video and the variable audio output circuits.
These switched voltages turn on given a DC level from pin 32 of IC6000. This signal will of course come
on when triggered by the power on key from the keyboard or the IR detector, IR6000. The DC level at pin
32 should be near +4.8 volts DC. This will drop across R3418 and switch the base of Q3402. As this
transistor turns on, it drives Q3404 into saturation and activates the switched voltages.
Degaussing Control
Degaussing is accomplished via software in the CA chassis. At turn on, pin 33 of IC6000 generates a +4.8
volt DC level. After dropping through R3419, this DC switches on Q3403 to allow current flow through
the degaussing relay, KX3401. With the relay now turned on, filtered AC line current travels into the
degaussing coil passing through the thermistor, THX3415. 760 milliseconds after power-up, the microprocessor sets the voltage to zero, and the relay opens cutting off AC to the coil.
3T8 -- To
Degaussing
Coil
+18 VSW
Degaussing
Control, Pin 33,
IC6000
KX3401
R3419
DX3405
2
THX3415
1
Q3403
Filtered
AC Line
<<Figure CA-5>>
CA-4
Microprocessor Control
Introduction
The CA chassis employs IC6000 as its microcontroller. All end user and servicer controls are accessed
using this IC. While most of its functions will be described in terms of how they are used by other devices in
the receiver, a number of facts concerning the microprocessor and its input devices will now be presented.
The microprocessor’s job is to communicate control instructions and feedback information to and from
various other processors and input devices in the set. These include the video, audio, PiP, audio & video
switch ICs, the tuner, the EEPROM, the keyboard and IR detector, and the reset IC. Some of these use a
direct connection via either switch, variable pulse, or DC level for communication. Others rely on the I2C
bus, also known as serial clock and data bus. IC6000 provides 2 sets of clock and data lines. The first set
is pins 37 and 39, and the second is on pins 36 and 38. The EEPROM and the factory setup connector,
4G9, are the only devices which receive clock and data pulses from the first set.
Input Devices
The IR detector demodulates pulses from the 40 kHz modulated carrier and sends the pulses to pin 15 of
the microprocessor. There a special algorithm interprets the pulses as the various commands they represent.
The keyboard is only slightly more complicated in its operation external to IC6000. It works by varying
voltage on only two input pins (7 and 8) using resistor networks. A/D converters inside the micro interpret
the different voltages. Because voltage detection is used rather than active keyboard scanning, keyboard
radiation is not a problem, but maintaining a +5VSB to within ±4% is critical.
+5VSBF
R6025M
R6024M
R6022M
R6020M
R6021M
R6023M
R6019M
R6070M
SW6
MENU
SW4
VOL-UP
SW5
VOL-DN
SW3
CH-DN
SW2
CH-UP
SW1
ON/OFF
R6018
R6069M
R6017M
Pin 7
R6015
+5VSBF
Pin 8
R6016
L6005
C6043M
2K6
C6035
PROV
R6029M
C6042M
Keyboard
& IR Input to
IC6000
C6036M
R6028
1
R6027
2
C6003M
3
3
4
VOUT
L6004
C6004
5
C6092M
EXTERNAL
KEYBOARD
Pin 15
2
VS
1
GND
IR6000
<<Figure CA-6>>
CA-5
CA CIRCUIT DESCRIPTIONS
For those CA chassis that have the keyboard and IR detector built onto the module, the schematics are
included. Keep in mind, however, that many of the various CA chassis have a keyboard and IR module that
is separate from the main board.
Microcontroller
VCC is provided to pin 27 of the microprocessor from the +5VSBF supply. While this voltage is relatively
low, IC6000 is fairly demanding in terms of current. This same voltage also powers the keyboard and IR
detector. Additionally, the +5VSBF is used as analog VCC and enters the micro at pin 18.
IC6002 serves as a reset IC for the main microprocessor. Note that it comes in a transistor type package.
It accurately resets the micro when SB voltage is detected. Pin 30 is the reset signal input for IC6000. The
micro enters reset state after detecting a low on pin 30 of 2µS or more.
When the micro receives a power on signal from either the keyboard or the remote, the degaussing control
pin 33 turns on the degaussing circuit for 760ms. At the same time a constant voltage level from pin 32
turns on the switched voltages in the power supply.
R6001M
FLYBACK
R6004M
R6003M
V-RAMP
V-DRIVE
C6001M
R6008M
C6024M
PROV
Q6001
R6005M
C6025M
PROV
R6002M
R+UP
G+UP
B+UP
FASTBLANK
HALFTONE
R6082M
C6033M
PROV
C6067M
R6084M
C6099
C6064M
R6083M
+5VSBF
IC6000
C6068M
D6002
Q6002
1 HSYNC
R6058M
R6090M
AFC
R6061M
SYNC
C6058M
G 51
3 AFC
B 50
C6062M
C6090M
11 PiP_BRT
CRT-PROTECTOR
MUTE
R6026
To IR6000
C6040M
C6092M
L6007
C6098
C6006
C6005M PROV
C6009
R6080
C6007M
R6033M
SCL2 38
16 NC
SDA1 37
SDA2 36
AUD-SWITCH
PiP-SWITCH1
AUX-SWITCH1
EEPROM
& Factory
Setup Ckt
C6046M
RADIO/TV 34
DEG-CTL 33
21 VHOLD
POWER 32
DEG-CTL
PWR-CTL
C6045M
R6036M
CHASSIS-ID 31
24 XIN
C6041M
IDENT 35
20 RVCO
23 CNVSS
C6018M
RESET 30
OSC-OUT 29
25 XOUT
26 VSS
CRY6001
C6094M
PROV
SCL1 39
15 REMOTE
22 CVIN
C6008M
PROV
C6055M C6095M C6038M
C6051M
AUX_SW1 42
H/T 40
19 HLF
R6032M
C6053M
C6052M
PiPSWITCH1 43
NC 41
18 AVCC
R6031M
VERT-SIZE
HORZ-SIZE
VOL-CTRL
NC 45
13 CRT-PROT
17 NC
R6030
C6037
C6057M
VOL 46
12 NC
14 MUTE
+5VSBF
R6081M
R6040M
AUD-SWITCH 44
10 Y/C-SENSE
C6061M
COMPOSITE
VIDEO IN
HORZ-SIZE 47
9 NC
R6053M
Y/C-SENSE
VERT-SIZE 48
6 SYNC
8 A/D_KEY1
C6093M
C6066
PROV
FB 49
5 NC
7 A/D_KEY2
To Keyboard
C6079M
R6012M
R 52
2 VSYNC
4 FM_SD
PiP-BAT
C6023M
Q6003
L6002
OSC-IN 28
VCC 27
CRY6002
PROV
R6035M
R6060M
C6015M
+5VSBF
+5VSB
R6034M
R6037M
L6001
C6010M
IC6002
C6011M
C6013
C6012M
VCC
C6017
R6059M
OUT
C6016
C6056M D6001
GND
C6014M
<<Figure CA-6>>
Horizontal and vertical synchronization pulses are fed into pins 1 and 2. These provide the microprocessor
the current sweep location of the beam, which is necessary to correctly interrupt main video for various
CA-6
Microprocessor Control
types of on-screen display (OSD). Neither sync pulses come directly from the video processor where they
are first produced. Horizontal sync is actually fed back from the sweep transformer on the flyback pulse
line. Vertical ramp signals feed the base of Q6002. Sync is produced on the collector and fed to the
vertical amplifier and through R6006M to the V-Sync pin of the micro. OSD or CC (closed captions) are
sent as processed RGB (red, green, & blue) from pins 50, 51, and 52. At those times it is necessary to
blank out main video, a fast-blank (FB) pulse is sent to the video processor from pin 49 along with the
processed RGB. An exception to this occurs when PiP is displayed. Under that circumstance, the fastblanking pulse without RGB is sent to the video processor.
Some CA chassis feature a halftone function that dims video surrounding OSD. This halftone circuit is
described in the video section, but is controlled by a DC level from pin 40.
Closed captioning display is accomplished in the microprocessor by use of the composite video into pin 22.
Here a data slicer extracts the caption information and outputs it to the RGB pins when captioning is requested by the user. Note that when OSD needs to be on the screen, such as after a channel change or
during a volume change, the OSD will have priority, and CC will mute. IC6000 also gains synchrony
information from the composite video stream.
Pin 6 is a signal detection pin. When the tuner sends a bona-fide signal to the video processor, it separates
the horizontal sync signal from the IF and sends it to this portion of the microprocessor. It can then be used
to determine if a certain channel is carrying an active broadcast.
Automatic frequency correction (AFC) is sent to the microprocessor via pin 3. The DC level on pin 3 tells
the microprocessor if it needs to communicate an adjustment to the tuner to allow for clearer channel
reception. The ideal voltage level here should be approximately +2.5 volts.
IC6000 provides CRT-protection for the set through pin 13. Operation of this shutdown depends on a DC
level from the CRT protection circuit off the vertical amplifier circuit. Should the vertical IC2100 fail, the
DC level will no longer be present. In this situation, the CRT-protection latch will shut the receiver down
three seconds after detecting the failure. This circuit will prevent the CRT from burning a horizontal phosphor line in the center of the screen or, worse yet, cutting the yoke end of the tube off completely.
The remainder of the input and output pins of IC6000 are adequately described in other sections of this
manual. Refer to the video, audio, and deflection sections of the CA chassis for these descriptions.
IC Location
Part #
Notes
IC6000
221-01384-01
221-01384-02 Refer to Service Manual
221-01386-01 for Corresponding Model
221-01387-01
IC6001
221-00745-04
All Models
IC6002
221-01177A
All Models
<<Table CA-1>>
CA-7
CA CIRCUIT DESCRIPTIONS
Memory
The EEPROM, IC6001, is a small but vital part of the CA receiver. This 512 byte memory chip is responsible for storing servicer adjustments, channel information, and user settings, even when power is removed
from the set. This information is transferred on the clock and data lines from the micro into pins 5 and 6.
The EEPROM is powered by the +5VSBF source at pin 8.
Clock & Data
for Tuner, Video
and Audio
R6047M
+5VSBF
R6046M
R6045M
DATA2
CLOCK2
4G9
R6048M
IC6001
4
5
3
6
2
7
1
8
R6050M
1
R6049
2
3
4
5
+5VSBF
R6044M
R6043
R6042M
R6041
R6039M
C6021M
C6050M
C6049M
C6048M
C6047M
R6072
L6003
C6020
39
CLOCK1
38
CLOCK2
37
DATA1
<<Figure CA-7>>
CA-8
36
DATA2
35
IDENT
C6019M
(IC6000)
IF Receiver
Tuner
Cable or off-air signals are received into the television by way of the antenna jack of the tuner, TU6000.
The input and output impedance of this device is 75 ohms. It provides for 181 channels (including cable).
It uses +33V for tuning, +5VTune as tuner B+, +4.3V for AGC, and on some chassis +9VSW.
As with standard varactor tuners, varying voltage across an internal varactor results in a different internal
resonant frequency, whereby tuning of the various channels is achieved. Control of this process is accomplished through the I2C (serial clock and data) lines attached to pins 4 and 5 of TU6000. These transfer
control data to and from IC6000.
AGC (automatic gain control) voltage is applied to pin 1 of the tuner from pin 3 of ICX2200. This DC
voltage varies in response to signal strength from the tuner so as to avoid signal distortion not only from low
signal levels, but also from signals strong enough to otherwise cause clipping distortion. AGC voltage will
alter the signal level accordingly.
+33V
TP6006
TP6005
IF
TU6000
11
ZD6001
C6032
10
C6031M
9
8
** ONLY FOR 175-2771 TUNER
7
+5VTune
6
J6000M **
5
4
C6030
C6029M
TP6004
3
TP6010
C6028
2
1
+9VSW
L6000
CX6027
C6090
PROV
C6070
PROV
RF-AGC
C6026M
Data2
Clock2
OMIT FOR 175-2771 TUNER
From Pins
36 and 38,
IC6000
<<Figure CA-8>>
IF Processor
Tuner IF (intermediate frequency) comes from pin 11 of the tuner. This is filtered and amplified (see
Q1200, U1200, and surrounding circuitry) before it is fed into pins 7 and 8 of ICX2200, the IF/video
processor (sometimes called the Jungle chip). IF consists of PIF (Picture IF), SIF (Sound IF), and CIF
(Chroma IF).
CA-9
CA CIRCUIT DESCRIPTIONS
IF
Composite
Audio
AGC
Pin 1,
TU6000
+9VPIF
R1202M
+9VSW
+9VPIF
R1225
R1200M
R1206M
L1200
C1200M
+9VSIF
L1203
R1201M
C1201M
L1202
C1218M
C1215M
C1216
3
L1204
2
C1202M
L1201
1
R1209M
R1204M
C1204M
U1200
1
Q1202
R1210M
TP1201
R1215M
4
R1220M
C1213M
Q1200
R1205M
2
5
ICX2200
1 NC
R1207M
R1203M
+9VSW
TP1200
R1208M
C1203M
C1208M
R1212M
R1211M
C1212
C1209M
C1210
+9VSW
3 RF-AGC
DE-EMPH 54
6 PIFGND
R1231M
C1207
EXT-AUD 55
5 AGC-FIL
R1213M
C1217M
AUDIN 53
L1205
C1214
SIFGND 51
PIFTANK 50
8 PIF-IN
PIFTANK 49
9 PIF-VCC
SIF-VCC 48
10 LOOPFIL
TV/DET 47
U1202
R1214M
U1201
TP1202
VCC 46
Q1201
C1211M
L1207
+9VSIF
C1219M
C1220M
C1222
R1221M
R1219M
LIMITER 52
7 PIF-IN
11 APCFIL
+9VF
TP1248 TP1245
NC 56
2 SND-OUT
4 SIF
C1206
+9VPIF
TVIN
C1205M
3
C2237M
R1218M
4
L1206
3
2
C1221M
6
R1216M
R1217M
1
<<Figure CA-9>>
ICX2200 powers its IF section using +9VPIF (pin 9) and +9VSIF (pin 48). The IC’s main VCC is a
+9VF supply to pin 46. IF signal continues from pin 47 at nearly 2Vp-p to an FM trap where SIF is
separated from PIF. SIF reenters ICX2200 at pin 52, the limiter. From this, composite audio is developed
and transmitted from pin 2 of the video processor to the audio circuitry. The remaining PIF passes through
Q1202 for de-amplification to 1Vp-p. The resulting signal, denoted TVIN, is passed to both the Jungle IC
at pin 37 and pin 5 of IC2902 (refer to the jack-pack and switching section below).
AFT (automatic fine tuning) is also derived from the video processor at pin 44. This signal feeds the microprocessor, IC6000, to generate minute tuning adjustments so as to maintain optimum channel quality.
Part Location Part #
Notes
TU6000
175-02721 Refer to Service Manual
175-02771 for Corresponding Models
ICX2200
221-01165
All Models
<<Table CA-2>>
CA-10
Video Processing
Introduction
ICX2200 has numerous duties involved in television image and sound production. As mentioned above, it
processes sound and video IF. Additionally, it prepares NTSC video utilizing separated chroma, luma, and
OSD from IC6000. Accounting for controlled preference information from the micro such as brightness,
tint, sharpness, contrast, etc... the “Jungle” chip then produces this video signal as RGB which is amplified
and sent to the picture tube. Finally, the video processor generates the very drive signals that cause the
deflection circuitry to operate and produce high voltage as well as picture.
A/V Switching
At this point, because of its interaction with the video processor, an explanation of the jack-pack switching
section is expedient. Depending on the extra features a CA receiver has (S-VHS Video or Y/C, PiP), the
chassis will have two switching ICs, IC2901 and IC2902. IC2902 is the PiP switching IC. The first
CM
Chroma-Comb
Aux Switch1
Ext Video
VIN PiP
TVIN
PiP Switch1
Y/C Sense
L2901
C2918
R2902M
R2905M
C2900
C2903M
W2903
12
+9VSW
11
C2914
C2906
10
CH-2
9
8
R2920M
C2904
C2911
C2913
J2902M
C2902M
R2919M
R2918M
7
6
C2912M
5
R2921M
CH-1
4
C2916
3
Q2902
R2901M
C2917M
2
ZD2902
1
R2922M
C2915M
IC2901
R2908
R2923M
C2909
12
R2909
11
C2910
10
CH-2
9
8
C2918
7
6
C2908
R2915M
5
VM Out-R
VM Out-L
Ext-R
Ext-L
3
2
R2914
1
R2907
C2907M
ZD2903
11
10
9
8
7
6
IC2902
R2911
R2910M
R2916
12
CH-1
4
R2917M
ZD2901
R2912
5
4
3
2
1
J1
External
Left
Variable Monitor
Out - Left
External
Right
Variable Monitor
Out- Right
Video-In
S-VHS
<<Figure CA-10>>
CA-11
CA CIRCUIT DESCRIPTIONS
switching channel of this IC switches the PiP between external and internal video sources based on the PiP
Switch1 signal (pin 4, IC2902) from the microprocessor. The internal video signal, denoted TVIN, is the
same signal as the one entering pin 37 of ICX2200. Whichever signal is selected is sent as VIN PiP to the
PiP module through pin 10 of the PIPA1 connector. The second switching channel of IC2902 allows
selection between composite video input and S-Video input. While normally it defaults to composite video,
its switching action is based on the presence of S-Video. The output of this switch feeds the external side of
the PiP switch.
IC2901 is referred to as the main switching IC. Both switching channels of IC2901 are controlled by the
AuxSwitch1 input from the microprocessor. It is tempting at first glance to assume that this IC switches
between external and internal video sources. However, ICX2200 actually handles that process internally.
Rather, IC2901 switches the between the external source to be viewed (composite or S-Video) on switching channel 2. The output from this channel goes to pin 39 of ICX2200, the external video input. Channel
1 switches between the internally separated chroma signal and the S-Video chroma signal, and feed its
output back to pin 45. See below for a further description of video separation.
Video Development
For video processing, ICX2200 will switch between tuner IF, which as discussed above enters the IC at pin
37, or an external video source, which enters the Jungle chip at pin 39. Switching between these will be
directed by the microprocessor via the I2C bus entering ICX2200 on pins 27 and 28. The selected signal is
emitted from the switched video out pin (41) as composite video. This signal is sent to the microprocessor
and the glass comb-filter, DL2200.
The purpose of the comb-filter is to separate chroma from luma. Its superiority to conventional filtering and
separation schemes is that it reduces cross talk between chroma and high-frequency luma. Historically, sets
without this feature were prone to have rainbow effects on objects whose luminance frequency approached
the 3.58 MHz color subcarrier. (Note that this frequency is established by CR2201, the color crystal in CA
chassis.) The result of the comb-filter’s operation is that cross color distortion is minimized for much more
highly detailed objects.
Composite video enters the comb-filter on pin 2. Luma is produced on pin 5 and is fed to pin 43. A
3.58MHz trap (C2229M, L2201, & R2245M) removes any residue chroma. Separated chroma exits the
comb-filter at pin 3. In sets that utilize IC2901 for jack-pack switching purposes, chroma from the combfilter is sent to pin 5 and exits at pin 8. This signal is then denoted by CM, and is passed back to the video
processor via pin 45. (In sets that do not use IC2901, chroma passes directly to pin 45.) A band-pass
filter (C2232M, R2253M, & L2202) eliminates any remaining luma.
Once inside the Jungle IC, luma is processed with numerous factors including contrast and brightness.
Brightness and contrast information from the beam current passes into pins 36 and 38 from the circuitry
consisting of Q2204, 2205, and 2209. ICX2200 responds to this information by limiting (when necessary)
contrast and brightness to the RGB outputs. Basically, the ABL responds to current from pin 8 of the
sweep transformer, TX3204. D2204, R2235, and C2220 make this signal positive. It is then inverted by
Q2205 and smoothed as it passes to Q2204. As beam current approaches 1.5 mA (1.3 mA on 25”, 0.9
mA on 19”/20”) Q2209 starts to turn on and shunts excess current to ground. In addition to controlling the
CA-12
Video Processing
RGB output, this circuit helps to prevent blooming. Excessive current draw in the picture tube will lower
voltage and hence decrease beam acceleration. This results in an increase of the sweep. Without ABL, the
blooming effect is usually seen when very bright images appear on the screen. ABL should prevent this and
extend the life of the picture tube.
C2235M
C2236M
R2254M
+9VF
+9VSW
L1207
C2232M
+9VF
R2252M
L2202
CM
C2233M
PROV
R2253M
PROV
Q2208
+9VF
R2261M
R2260M
C1220M
C1222
R2262M
TP1203
R1223M
AFC
R1222M
C2253 PROV
ICX2200
W2207
R2251
C1223M
12 VCXO
CIN 45
13 GND
AFT 44
14 FBLNK
YIN 43
15 ROSD
DC 42
16 GOSD
VSW-OUT 41
17 BOSD
BLK/DET 40
18 D-VCC
VIN 39
19 ROUT
ACL 38
20 GOUT
TV-IN 37
21 BOUT
ABL 36
C1224
CHROMACOMB
R1224M
C2228M
C2231
3
R2244M C2232
C2229M
R2245M
L2201
W2206
DL2200
2
5
+9VSW
+9VSW
C2224
C2230
C2225
R2246M
1
R2250M
+9VF
C2223
R2236M
R2248M
C2227
R2242M
R2239M
4
TVIN &
AMP CKT
(Pin 47)
Q2211
PROV
W2200
R2249M
+15VSW
C2222
C2221
D2205
D2202
+15VSW
R2243M
R2247M
R2270
Q2206
+15VSW
EXTVIDEO
Q2209
R2241M
R2240M
R2265M
COMPOSITE
VIDEO-OUT
R2237M
R2264
D2203
Q2205
R2238M
D2204
Q2204
R2263
C2241
VERTICAL
ABL
R2234M
C2218
R2235
R2232M
R2233
ABL
C2219
R2230M
C2220
<<Figure CA-11>>
Before sending processed RGB (red, green, & blue) outputs to the picture tube, ICX2200 integrates any
OSD (on-screen display), CC (closed caption), and PiP (picture in picture) into the video. At a particular
point in the television’s scan across the picture tube, where the video is to display an OSD object, a fastblanking (FB) pulse is sent from the microprocessor to the video processor at pin 14. This pulse of course
blanks the main screen video so that OSD can have precedence. Simultaneously, processed RGB from the
microprocessor enters the Jungle chip at pins 15, 16, & 17. This video fills in the blanked portion to be put
onto the main screen.
Picture-in-Picture
A few notes concerning PiP are noteworthy here. First those sets that have PiP will not be able to produce
video without the PiP module installed unless the PiP section is jumpered out. J2201M, J2202M, W2203,
and W2204 accomplish this. PiP signal enters the PiP module at pin 10 of connector PIPA1. This signal is
converted into RGB by the PiP processor and sent on to RGB OSD inputs of ICX2200. Pins 2 and 3 of
CA-13
CA CIRCUIT DESCRIPTIONS
the PIPB1 connector provide sync to the PiP processor. Pins 9 and 10 of the same connector allow I2C
bus communication between the PiP board and the microprocessor. PiP brightness however is controlled
from pin 11 of the microprocessor. This controls the bias of Q2210, which varies a DC level on the OSD
input lines to ICX2200.
PIPA1
PiP+SW
1
2
3
4
5
6
PiP Brt
7
8
9
10
+9VSW
FASTBLANK
G+UP
R2201M
R2205M
R2267M
C2239
R2268M
B+UP
R2207M
R2202M
R+UP
J2201M
Q2210
R2771
PROV
C2242M
R2203M
R2204M
R2206M
ICX2200
W2204
R2208M
D2212
J2202M
C2240
D2211
C2202M
R2269M
D2210
W2203
C2203
C2204
C2205
C2206M
PIPB1
1
2
3
4
5
6
7
8
9
10
+9VSW
C2207
+5VTuner
+9VSW
R2210
CR2201
12 VCXO
CIN 45
13 GND
AFT 44
14 FBLNK
YIN 43
15 ROSD
DC 42
16 GOSD
VSW-OUT 41
17 BOSD
BLK/DET 40
18 D-VCC
VIN 39
19 ROUT
ACL 38
20 GOUT
TV-IN 37
21 BOUT
ABL 36
FLYBACK
VRAMP
R2219M
R2215M
R2209M
SCL
SDA
Q2201
R2213M
D2209
R2258M
D2208
R2257M
D2207
R2256M
5
Q2202
R2218M
4
2C5
HALFTONE
Q2207
3
2
1
Q2203
R2211M
R2217M
R2222M
R2221M
C2240M
PROV
C2238M
R2255
<<Figure CA-12>>
After PiP or OSD RGB enters the Jungle IC, it is combined with processed luma and chroma and then exits
ICX2200 as main video for the picture tube. Red, Green, and Blue outputs are found on pins 19, 20, and
21. Some CA receivers have a halftone circuit that taps off these lines. When Q2207 is switched on by a
signal from the microprocessor, a limited amount of RGB signal is shunted to ground. The on-screen effect
of this is a slightly dimmed video. This halftone signal is output in such a way to appear as a darkened but
transparent window surrounding the OSD.
Video Amplification
Before being fed into the CRT socket board via connector 2C5, RGB is pre-driven by Q2201, Q2202,
and Q2203. The resulting signals are then sent to the main color driver transistors, Q5101, Q5102, and
Q5103. These transistors have a high 300V collector to emitter breakdown voltage and a low collector to
base feedback capacitance (less than 3pF). Additionally, the series-parallel arrangement of both their
emitter and base circuits involving both capacitors and resistors allow for improved high and low frequency
response. The cutoff frequency of these drivers is 70 MHz. R5103, 5110, and 5119 from base to collector
help to increase bandwidth response of the drivers. These provide negative feedback from the output and
decrease gain. As gain decreases however, bandwidth response increases. The driver transistors are
CA-14
Video Processing
powered by the +215V source derived from the sweep transformer, but the actual DC voltage at the
collectors will be lower (+130 volts is a good ballpark figure) because of the resistors RX5104, 5111, and
5122 and variations in the drive signal.
L5103
1
+215V
L5101
RX5104
2
5F2
R5107
R5103
C5101
+9 VSW
DAG
R5101M
1
Q5101
5C2
R5102M
2
2
2
3
C5104
C5102M
1
C5103M
G2 Wire
to Sweep
2
4
R5105M
2
1
Red
R5106M
3
R5116
BLUE
D5102
PROV
4
RX5111
GREEN
5
G2
9
8
10
Blue
RED
R5110
R5115
Green
7
11
6
12
5
R5108M
R5124M
PROV
4
G1
Q5102
1
R5109M
CRT1
R5128
PROV
W5101
R5114
Q5104
PROV
C5106M
RX5122
C5105M
C5110
PROV
2
R5112M
R5127
R5113M
R5125
PROV
R5123
R5119
D5101
+215V
C5107
R5117M
Q5103
C5109M
1
R5126
R5121M
R5118M
C5111
L5102
C5108M
R5120M
2
<<Figure CA-13>>
The emitter circuits of each driver are attached not to ground, but to a reference voltage of about +3V. This
reference voltage is established by R5114 and D5101 and serves to set a black level for the cathodes
around +165 volts. The reference voltage must be relatively noiseless, so C5107 is used to eliminate any
interference.
A number of the CA chassis provide an afterglow cutoff circuit on the CRT socket board. This circuit
makes use of the fact that with respect to the picture tube, G1 is the ground. Because C5107 takes a
relatively long time to discharge, there is the possibility that the picture tube could continue producing
electronic emissions for a short time after the receiver is turned off. The afterglow cutoff makes use of
power from the filament voltage (pin 4, connector 5F2). When the receiver turns off, the loss of this voltage
turns off Q5104. This allows for a brief moment the G1 cathode to become more positive, leaving less
potential on the other cathodes from any remaining voltage across C5107. C5110 determines the dead time
on response, and C5111 determines the rise time of the G1 voltage, both of which are between 10 and 30
milliseconds.
CA-15
CA CIRCUIT DESCRIPTIONS
Deflection Processing
The last portion of the video processor to be discussed is the deflection section. This is the part of the IC
from which the vertical and horizontal deflection signals are derived. A critical power supply to this section
is the +9VSW which feeds pin 26. Pin 24 emits the V-Ramp signal, from which both vertical sync for the
microprocessor and vertical drive for the vertical amplifier are developed. Refer to Q6002 in the microprocessor circuit for this process. Horizontal drive comes from pin 32. This ultimately drives the horizontal
output transistor, which provides both horizontal deflection and power for the sweep transformer. Pin 31
provides the sync pulse output to IC6000. This signal is really the horizontal sync pulse separated from the
rest of the video signal. It allows the microprocessor to determine whether or not the receiver has a valid
signal. The flyback pulse is input to pin 30, thus allowing sweep feedback to the video processor’s deflection section.
+9VSW
R2229M
ICX2200
R2216
C2217M
22 VPULSE
R2212M
VRAMP
C2208
C2209
C2210M
23 NFB
32FH 34
24 VRAMP
HAFC 33
25 VSEPFIL
26 HVCC
R2220
R2223
C2211M
PROV
DGND 35
CR2202
C2215M
H-OUT 32
FLYBACK 30
28 SDA
SHUTDOWN 29
C2212M
PROV
R2231M
H-SYNC 31
27 SCL
D2201
C2216
R2225M
C2213M
CLOCK
DATA
C2214M
R2224M
C2554
PROV
R2226
FLYBACK
SHUTDOWN
H-SYNC
H-DRIVE
R2227M
<<Figure CA-14>>
High-Voltage Protection
The last terminal of note here is pin 29, the x-ray protection/shutdown pin. If the potential at this pin rises
above +3.5 volts DC, the video processor will automatically clamp the horizontal output signal, shutting
down the receiver. In the event that this occurs, the microprocessor will have to be reset before the television can be powered up again. Voltage at pin 29 is based on the voltage output from the flyback. High
voltage shutdown will correspond with an over-voltage in the picture tube, which could otherwise begin to
emit x-radiation.
CA-16
Deflection Control
Introduction
After deflection control signals are produced by ICX2200, they need to be modified and amplified before
they are output to the deflection yoke. The CA chassis accomplishes this necessity for 25” to 36” television
sets through the sweep transformer and the surrounding horizontal and vertical deflection circuitry.
Horizontal Drive
The Horizontal Drive (H-Drive) circuitry exists to control the drive signal to the Horizontal Output Transistor
(HOT) as well as provide deflection to the horizontal yoke. Typically H-Drive operates at 15.734 kHz. As
it passes through the driver circuit, H-Drive signal is amplified to provide a sufficient signal to the HOT
without causing it to go into saturation, thereby preventing distortion of the drive signal. H-Drive is produced at pin 32 of the Video processor (ICX2200) and is passed to the drive circuit through R2227M, a
surface mounted resistor. The signal enters the base of Q3201 which is directly coupled through its emitter
to Q3202. Finally, the signal passes from the collector of Q3202 to the Horizontal Driver Transformer,
TX3205, where voltage-to-current conversion and proper waveshaping occurs.
+18 VSW
RX3207
R3203
H-Output to
Flyback & Yoke
CX3205
R3204
R3205
QX3203
TX3205
CX3212
C3201
H-Drive from
Pin 32, ICX2200
C3203
Q3201
1
6
C3206
C3202
5
3
Q3202
C3204
Flyback Line to
Pin 30, ICX2200
4
LX3202
R3201M
R3202M
<<Figure CA-15>>
Flyback Transformer
From here, the signal switches the HOT (QX3203) on to provide a current shunt for the sweep transformer,
TX3204 and the horizontal yoke. This switching alternately passes then blocks the B+ voltage provided
through the primary winding of TX3204 to the collector of the HOT. The changing magnetic field in the
sweep transformer caused by this action generates the high voltage (HV). This high voltage should normally
be between 26 and 30 kV. The particular value will correspond to the size of picture tube in the set. G2
(screen control) and Focus voltages are tapped from a portion of the same winding that HV is derived from.
As usual G2 and Focus may be adjusted by pots on the sweep transformer. These run to the CRT socket
board.
CA-17
CA CIRCUIT DESCRIPTIONS
A number of secondary voltages are also provided by the sweep transformer’s action. Particularly, +215
volts is supplied from pin 2 to the Video Output circuitry for driving color. In addition, +35V and +25V are
supplied, respectively from pins 6 and 9, for horizontal width and pincushion control circuitry (when necessary) and for vertical amplification circuitry. Filament voltage is also supplied from pin 7 into pin 1 of
connector 2F5. Two other signals from the flyback are the ABL (pin 8) and the flyback pulse derived from
pin 6. Refer to the video processor section for an explanation of these signals.
ABL
+215V
H-Output
D2104
GND
E
+25V
8
G2
C2112
FOCUS
RX2124
+215 V
CX3208
RX3208
TX3204
C3209
4
To Video
3 Output
RX3217
9
HV
B+
2F5
C2111
DX3201
1
5
2
7
3
6
2
RX3210A
PROV
1
RX3209
CX3207A
+33V
+35V
CX3207
PROV
RX3211
DX3252
RX3216
CX3212
CX3254
RX3212
CX3253
DX3204
Flyback
Pulse
C3219
To HV ShutDown Circuit
<<Figure CA-16>>
High Voltage Shutdown
Another winding from the flyback is used for high-voltage shutdown, commonly referred to as x-ray protection. Activation of the HV shutdown circuit will occur when it detects a 4 to 6 kV increase in the high
From Flyback
RX3211
DX3006
CX3007
RX3013
PROV
RX3022
RX3016
To Shutdown
Pin 29, ICX2200
RX3015
PROV
+35V
CX3254
DX3252
CX3003
RX3010M
ZDX3004
DX3005
CX3253
RX3008
<<Figure CA-17>>
CA-18
RX3009M
CX3004
Deflection Control
voltage. The HV shutdown circuit utilizes a rectified DC voltage across CX3003. This voltage is applied to
a zener diode, ZDX3004, through a voltage divider consisting of RX3013, RX3015, RX3016, and
RX3022. The actual value of the zener will vary according to screen size. When this DC voltage becomes
high enough, the zener begins to conduct. The resulting voltage can be metered at pin 29 of ICX2200. If
the voltage in the shutdown pin is above +3.5 volts, the IC’s internal shutdown circuitry will trigger and
deactivate all horizontal signal from the IC, thereby shutting off the set. In this case, the microprocessor will
have to be reset before the television can be powered on.
Width and Geometry Correction
Width and east/west pincushion correction circuitry may be found on receivers with 27 - 36 inch picture
tubes. Smaller sets have pincushion correction preset in the windings of their deflection yokes. Otherwise,
width is controlled in the CA chassis digitally through the microprocessor, IC6000, using an internal pulse
width modulator. The width control signal is emitted from pin 47 of the microprocessor and is supplied to
C3250. This operation is very similar to the vertical size adjustment. The resulting DC voltage effects the
biasing of transistor Q3250, thereby changing the current in coil LX3201 and ultimately altering the width.
<<Figure CA-18>>
Vertical
Parabola
DX3203
R3258
RX3214
C3255
R3252
TP3200
R3257M
RX3215
W3201
LX3201
R3259
C3217
CX3218
CX3215
LX3262
Horz Size Pulse
+35V
W3200
C3250
W3202
CX3251
DX3251
DX3250
H Yoke
R3253
CX3252
RX3256
Vertical Rate
Drive
CX3216
QX3251
Q3250
CX3256
W3203
R3255
H-Output from QX3203
The pincushion correction is accomplished using diode modulation. Key components of this circuit include
the width coil, LX3201; the horizontal yoke; CX3216 and CX3252; CX3217, used for S-correction;
LX3262, for linearity; DX3250 and DX3251 as dampers; and QX3251 and CX3251, used for amplifying
the vertical parabola waveform. This circuit uses the parabolic waveform from IC2100, the vertical amplifier, to shorten the horizontal scan lines on each end of the vertical trace. As the vertical trace is near its
extremes, voltage across CX3251 is increased. The result is a lower net voltage across the horizontal yoke
coil which translates to less beam deflection. Conversely, when QX3251 modulates a lower voltage across
CX3251, particularly when the vertical scan is closer to the middle of its trace, deflection is increased. The
CA-19
CA CIRCUIT DESCRIPTIONS
resulting waveform for yoke current is a sawtooth with rounded peaks.
Vertical Amplification
Most of the vertical signal amplification is performed by the vertical amplifier, IC2100. This IC contains a
power amplifier, a ramp generator, and a flyback generator and is supplied by +25 volts to pin 10. The
initial vertical drive signal which should run at 60 Hz is developed from ICX2200, the video processor. Pin
24 of ICX2200 is the vertical ramp (VRamp) source. This signal is inverted by Q6002 and sent as vertical
sync to pin 2 of IC6000. It also travels as vertical drive to pin 3 of IC2100 through R2101. The vertical
output signal to the yoke comes from pin 1.
<<Figure CA-19>>
+25 V
DX2101
CX2110
To CRT
Protection
Circuitry
IC2100
CX2105
10
11
2
Vertical
Drive
R2101
3
Flyback
Generator
Ramp
Generator
Vertical
Size
R2103
Clock
Pulse
R2104
4
C2101
Vertical
Output
R3
Power
Amp
1
Voltage
Regulator
C2130M
7
Vertical
ABL
R2105
6
RX2117
Buffer
Stage
Thermal
Protection
R2118
R2119
C2106
R2106M
8
R2107M
9
R2114
5
R2112M
R2109M
C2102
C2107
R2110M
C2103
C2104
C2108
R2113
R2108
R2111M
RX2115
RX2116
Vertical Rate
Drive for Pin
Correction
Vertical size is also amplified within IC2100. IC6000 controls vertical size using a pulse width modulated
signal emitted from pin 48. The signal generates a DC voltage across C2101. This DC controls vertical
height using circuitry inside IC2100. As the width of the pulse changes, a corresponding change occurs in
the DC level. In this manner, vertical size may be controlled in the on-screen servicers menu.
CA-20
Deflection Control
CRT Protection
CRT protection is provided for the CA in circuitry off the vertical amplifier. In case of a damaged IC2100
or a shorted CX2107 for example, this circuit will prevent damage to the CRT by shutting the microprocessor off. In turn, this action shuts down the television receiver. The circuit is composed of C2109, DX2102,
DX2103, R2120M, R2121, R2122M & R2123. Pin 11, the pump-up, of IC2100 emits a pulsing waveform. DX2102 rectifies this waveform to a DC voltage across C2109. After passing through the voltage
divider network formed by R2121 and R2122M, the voltage can be found on pin 13 of IC6000 and should
meter between +3.6 and +5.1 volts. Should the voltage be outside this range, CRT protection will trigger.
If the CRT protection circuitry is triggered at power on, the television will turn off in 3 seconds. If this
occurs, it will be necessary to reset the microprocessor before the television will turn on. Resetting the
microprocessor may be accomplished by removing AC to the set for a couple minutes.
+5 VSB
Pin 11,
Vertical Amplifier,
IC2100
R2120M
DX2103
DX2102
R2123
R2121
C2109
To CRT Protection
Pin 13, IC6000
R2122M
<<Figure CA-20>>
Part Location
Part #
Notes
TX3204
095-04372-01 Refer to Service Manual
095-04601-01 for Corresponding Models
QX3203
121-01383
All Models
IC2100
221-00992-01
All Models
<<Table CA-3>>
CA-21
CA CIRCUIT DESCRIPTIONS
Audio Amplification
There are three audio circuit configurations used in the various CA chassis: mono, stereo, or MTS (Multichannel Television Stereo). While few CA receivers are monophonic sets, the mono audio circuit bears
mentioning due to the fact that it is used in each of the three circuit variations.
IC804, the audio amplifier IC and heart of the mono audio circuit, is capable of both mono and stereo audio
amplification. IC804 has dual audio inputs (pins 2 and 5) and, naturally, dual outputs (pins 10 and 7).
These outputs drive 8-ohm, 5-Watt speakers. The audio amplifier utilizes +18 volts audio (+18 AUD) as its
power supply on pin 9. Its characteristic voltage gain is 50 dB. However, to eliminate potential noise
problems, R854M and R864M are used in conjunction with feedback capacitors C852 and C862 to limit
voltage gain. Such an arrangement allows use of a higher power audio signal that is less prone to noise
interference. Maximum output to the speakers should not be more than 3 Watts. Pin 3 of IC804 connects
the Mute line from pin 14 of the microprocessor to the audio circuit. A high signal on the base of Q800 will
turn that transistor on, lowering voltage on pin 3 and causing the amp IC to mute the audio.
R843
+18VAUD
Mute
Q800
C843
C842
C841
C862
R864M
C864
Composite
Audio or Right
Audio
W140
3
C861
9
10
1
1
R861M
2
C851*
Left Audio
*(MTS or
Stereo Only)
9S4
IC804
2
5
R851M *
6
C855M
R852M
R862M
C865M
C863
4
8
7
3
C854
4
C852
R854M
R863
C853
To TV
Speakers
R853
<<Figure CA-21>>
When IC804 is used as a mono amplifier, composite audio comes through C861 into pin 2. When used in a
stereo or MTS receiver, pin 2 serves as the right audio channel input, and pin 5 as the left. C861 and C851
(for non-mono sets) are used to pass audio but block any DC. Surface mounted capacitors, C855M and
C865M, are used to set the gain cut frequency to approximately 13 kHz. Voltage dividers consisting of
R861M and R862M for the right channel and R851M and R852M for the left channel limit the maximum
signal input to 42 mVrms. Maximum output from the stereo processor is normally 490 mVrms, which
would be too high an input for IC804.
CA-22
Audio Development
In the mono circuit, composite audio is fed directly from pin 2 of ICX2200 into the audio amplifier circuit.
However, on stereo and MTS models, composite audio is fed into IC1400A or IC1400 respectively. Here
the composite sound can be separated into left and right audio channels.
Stereo Processing
In stereo receivers, IC1400A receives composite audio through C1436 into pin 11. Because the 490
mVrms composite audio signal from ICX2200 is too high for the audio processor input, the voltage divider
consisting of R1421M and R1422M limit the signal to 245mVrms. This audio processor is controlled by
the microprocessor via serial clock and data lines connected at pins 3 and 4. IC1400A is powered by the
+9VSW at pin 16. Its right and left channel output exit the IC at pins 1 and 2.
To Audio
Amp IC
+9VSW
C1415
R1405M
C1414
C1417
30 NC
LSOUT-R 1
29 NC
LSOUT-L 2
28 VCAWGT
SDA 3
27 VCATC
SCL 4
26
25
C1419
R1407M
R1408M
C1422
C1424
24
23
22
C1426
21
20
C1428
19
C1427
18
17
16
C1433M
C1430
VCAIN
VEOUT
VETC
DGND
MAININ
MAINOUT
VEWGT
PCINT1
VE
PCINT2
SAPIN
PLINT
SAPOUT
COMPIN
NDISETC
VGA
STIN
IREF
SUBOUT
GND
VCC
SAPTC
C1434M
PROV
C1435M
PROV
R1401
R1402
R1425M
5
C1421
6
7
Clock &
Data Lines
C1416
R1406M
8
C1420
9
C1418
10
11
C1413
12
13
R1404M
R1422M
14
15
R1421M
C1436
C1425
Composite
Audio In From
ICX2200, Pin 2
IC1400A
<<Figure CA-22>>
External audio input on the stereo chassis is passed to the audio amplifier via IC1401, a microprocessorcontrolled switching IC. This IC is powered by the +9VSW at pin 9. When the external inputs are present
on a receiver, processed audio from IC1400A will come into the switching IC at pins 5 and 12. External
(or auxiliary) audio enters the switching IC at pins 7 and 10. If an auxiliary source is detected by IC6000, a
signal from pin 44 of the micro will trigger pins 2 and 4 of IC1401 to switch from internal to external audio
inputs. Whichever audio source is selected will be passed from pins 8 and 11 to the volume control
IC1402.
CA-23
CA CIRCUIT DESCRIPTIONS
+18AUD
Audio Output
R to IC804
L
R1417
ZD1405
C1439
4
5
3
6
2
7
1
8
C1437
C1423
IC1402
C1429
+9VSW
* For Stereo Chassis
excluding 9-2064, 2065
C1455
12
11
C1409
10
J1406M *
R1418M
Left & Right
Stereo Audio
(Pins 1,2, IC1400A)
CH-2
9
+5VSBF
8
C1410
7
J1407M *
6
C1456
5
CH-1
4
D1401
Volume Control
Pin 46, IC6000
3
2
R1412
1
R1420M
R1413
C1438
R1419M
IC1401
R1418
Provisional on 9-2064, 2065
External Audio
from Jack Pack
Audio Switch
Pin 44, IC6000
<<Figure CA-23>>
IC1402 is powered by the +18AUD at pin 4. Pins 5 and 8 receive the audio input, while the output for
right and left channels come from pins 1 and 3 respectively. This volume IC is controlled by a DC level
from pin 46 of the microprocessor. Pin 46 emits a pulse width modulated signal that is rectified and
smoothed by D1401, R1420M, and C1438. The resulting DC voltage is applied to pin 7 of IC1402. This
voltage will vary from +0.5 to +5 volts DC. The gain of this IC is 12dB.
IC Location
IC804
IC1400
IC1400A
IC1401
IC1402
Part #
Notes
221-00598-01
All Models
221-01127
MTS Models
221-01382
Stereo Models
221-01171
Stereo Models
221-01380
Stereo Models
<<Table CA-4>>
CA-24
Audio Development
MTS Processing
For MTS chassis, IC1400 serves as the sound processor. It features mono, stereo, or SAP settings. It
also features adjustable bass and treble levels, balance adjustment, sound-right audio limiting, front surround
sound, and speaker cut-off. Furthermore, whereas internal and external source switching is accomplished
by a separate switching IC for the stereo sets, the MTS is capable of internally switching between various
sources.
<<Figure CA-24>>
External
Audio In
C1401M
C1403M
R1413
R1412
C1406M
C1431M
C1409
C1410
48 BASSL1
BASSL2 1
47 BASSR2
TRE-R 2
46 BASSR1
TRE-L 3
45 SURRTC
SURRIN 4
44 TVOUT-L
SURROUT 5
43 TVOUT-R
LSOUT-R 6
42 AUX2-L
LSOUT-L 7
41 AUX2-R
NC 8
40 AUX1-L
SDA 9
R1409M
C1415
38 VLTC
DGND 11
37 VLDC
SAD 12
36 VCAWGT
C1414
C1419
C1422
R1408M
C1424
NC 15
33 VEOUT
PCINT1 16
32 VETC
PCINT2 17
31 VEWGT
30 VE
C1426
C1428
C1435M
PROV
R1425M
C1434M
PROV
C1421
29 SAPIN
VGR 20
28 SAPOUT
IREF 21
26 STIN
C1416
R1406M
R1421M
C1436
C1413
R1404M
R1422M
GND 22
SAPTC 23
25 SUBOUT
C1420
C1418
PLINT 18
COMPIN 19
27 NOISETC
C1427
To Audio &
External Amps
MAININ 13
34 VCAIN
R1407M
R1402
R1401
C1404M
MAINOUT 14
35 VCATC
C1417
C1402M
SCL 10
39 AUX1-R
C1432
R1405M
Clock &
Data Lines
+9VSW
Composite
Audio In From
ICX2200, Pin 2
C1425
VCC 24
IC1400
C1430
C1433M
IC1400 is powered by the +9VSW at pin 24. Composite audio enters through C1436 at pin 19. This
signal is reduced by a voltage divider consisting of R1421M and R1422M. I2C bus control (serial clock
and data) from the microprocessor enters the MTS processor at pins 9 and 10. Information on these lines
controls those adjustments as described above as well as the volume. Right and left channel auxiliary input
feeds into pins 39 and 40. Audio outputs come from pins 6 and 7 and feed the amplifier circuit in the
manner described above.
CA-25
CA CIRCUIT DESCRIPTIONS
External Audio Output
The output pins here also feed the variable audio output circuitry. This common emitter amplifier has a gain
of 12 dB. Q1402 and Q1403 are used to amplify left and right channels respectively. Power for this
amplification stage is provided by Q1401, which uses the +15VSW. To reduce popping on the monitors,
the switching of Q1401 is briefly delayed by an RC network formed by R1440M and C1440.
<<Figure CA-25>>
L(7)
Stereo Signals
from IC1400,
Pins 6 & 7
+15VSW
R(6)
R1440M
R1441M
Q1401
VM-OUT-R
C1440
J1450M
PROV
R1447M
R1443M
R1448M
C1446
J1402M
PROV
R1451
R1442M
Q1403
R1446
VM-OUT-L
Q1402
R1449M
R1444M
C1444M
C1441M
R1450M
CA-26
C1443
C1445
R1445M
C1442
Flowcharts
Start
1. No Power
Is AC
connected?
No
Plug receiver
into AC source.
Yes
Does FX3401
conduct?
Replace
FX3401.
No
Yes
Is B+ present
at CX3420?
No
Yes
Replace
FX3402.
No
Is pin 3,
ICX3400
switching?
Does FX3402
conduct?
Yes
Yes
Is +18VSB
present across
CX3424?
No
No
Is QX3401
shorted?
Yes
Replace
TX3401.
Replace ICX3400,
QX3401, DX3406,
DX3407, DX3408.
Yes
Is +5VSB
present across
C3426?
No
Replace
ICX3402.
Yes
Does pin 32,
IC6000 emit a
DC pulse at
startup?
No
Replace
IC6000.
Yes
Is +18VSW
present across
CX3430?
No
Check Q3404,
Q3402.
Yes
Is +9VSW
present across
C3429?
No
Replace
ICX3401.
Yes
Is Horz & Vert
drive present
on pins 32, 24
of ICX2200?
No
Replace
ICX2200.
Yes
Refer to shutdown
troubleshooting.
CA-27
CA TROUBLESHOOTING
2. Shutdown
Start
Does the set
power up for
more than 2
seconds?
No
Yes
No
Does the DC
level at pin 29,
ICX2200 rise
above 3.5 volts?
Yes
Check HVshutdown circuit,
sweep
transformer.
Does the set
shutdown after
just 3 seconds?
Yes
Check IC2100 &
CRT protection
circuit.
Is B+ running at
a constant DC
level?
Yes
CA-28
No
Replace
ICX3400
No
Check
microprocessor
ciruitry.
Flowcharts
3. No Tuning
Start
Are all tuner
voltages
present? (Refer
to schematics.)
No
Check tuner
power supplies.
Yes
Is IF present at
pin 11, TU6000?
No
Does changing
the tuner fix the
problem?
No
Check clock and
data lines.
Replace IC6000
if clock & data
lines OK.
Yes
Is IF present at
pins 7, 8,
ICX2200?
No
Check IF line.
Replace Q1200,
U1200 if
necessary.
Yes
Is IF present at
pin 47,
ICX2200?
No
Replace
ICX2200.
Yes
Does Q1201 test
OK?
No
Replace Q1201
Yes
Refer to No Audio and No
Video Troubleshooting.
CA-29
CA TROUBLESHOOTING
4. No Video
Start
Is raster present
on the screen?
No
Yes
Check Q1201,
Q1202
No
Is there video at
pin 37, ICX2200?
Is 1.07 kVp-p
signal present on
collector of HOT?
No
Is regulated B+
present across
CX3420?
Yes
Yes
Check TX3204.
Check HOT and
H-drive circuit.
No
Check power
supply.
Yes
Is composite
video present on
pin 41, ICX2200?
No
Replace
ICX2200.
No
Check Q2206
and/or DL2200.
Yes
Is 0.76 Vp-p luma
signal present at
pin 43, ICX2200?
Yes
Yes
Are RGB signals
present on pins
3-5, connector
5C2?
No
Are Q2201, 2202,
2203 OK?
Yes
Is +215 VDC
present across
C5101?
Yes
Check G2
adjustment.
CA-30
No
Check TX3204.
No
Replace Q2201,
2202, 2203.
Flowcharts
5. No Audio
Start
Is +18AUD
voltage present
on pin 9, IC804?
No
Check audio
power supply.
Yes
Does Q800 test
OK?
No
Replace Q800.
Yes
Does DC level
change at pin 14,
IC6000, when
speaker cut-off is
toggled?
No
Replace IC6000.
Yes
Is composite
audio present at
pin 2, ICX2200?
Check
composite audio
line.
Replace
IC1400(A).
No
No
No
Does Q1201 test
OK?
Yes
Yes
Is composite
audio present at
Comp-In pin of
IC1400(A)?
Is +9VSIF
present on pin
48, ICX2200?
Yes
Yes
Is audio present
on LSOut-R/L
pins of
IC1400(A)?
No
No
Replace Q1201.
Check power
supply.
Replace
ICX2200.
Yes
Is audio entering
IC804 at pins 2,
5?
No
Check L/R audio
lines.
Yes
Replace IC804.
CA-31
Section 2:
CB Chassis
CB Chassis Safety Guidelines
X-RADIATION
Observe the Anode voltage meter reading and compare with the
table below for the proper CRT screen size. If the voltage reading is
higher that the maximum, verify circuit component values and proper
operation.
To prevent possible exposure to radiation caused by excessive CRT
Anode voltage, the CB Chassis incorporates a “High Voltage Shutdown” circuit. This circuit senses the level of flyback pulse from
“Flyback Transformer” representative of the actual high voltage on
the CRT anode. When this level exceeds a predetermined voltage,
the circuit shuts down the horizontal drive, preventing further generation of anode voltage. In this condition, the horizontal drive is
“latched” off. The drive will remain off until the microprocessor is
reset.
7'6))2
&:('
,:231 ,:1%<
7->)
&)%1
/:
/:
'31432)280):)06)4%-6
13(90)0):)06)4%-6320=
SHUTDOWN CIRCUIT OPERATION
This shutdown circuit operates by means of sample HV taken from
pin 6 of the sweep transformer TX3204. This sample of voltage is
rectified, filtered and compared with a reference voltage(fixed by
ZDX3004 by the transistor QX3002. When the HV reaches the maximum permitted voltage, the transistor QX3002 enters in conduction
mode like consequence the transistor QX3001 also enters in conduction. When QX3001 enters in conduction, the flyback pulses at the
entrance of the video processor are 1 volt or less,the the TV goes out
and enters in shutdown mode.
SAFETY CIRCUIT TEST PROCEDURE
This shutdown circuit operates by means of a sample of HV taken
from pin 6 of the sweep transformer TX3204. This sample of voltage
is rectified, filtered and compared with a reference voltage ( fixed by
ZDX3004) by the transistor QX3002. When the HV reaches the maximum permitted voltage, the transistor QX3002 enters in conduction
mode; like consequence the transistor QX3001 also enters in conduction.
When the shutdown circuit is operating, the microcontroller will
prevent the TV from being turned on again unless the microcontroller
has been restarted by disconnecting the TV from the AC line.
CRT ANODE HIGH VOLTAGE MEASUREMENT PROCEDURE
When QX3001 enters in conduction, the flyback pulses at the entrance of the video processor (pin 18) are attenuated. If this
atenuattion is so that the flyback pulses at the entrance of the video
processor are 1 volt or less, then the TV goes out and enters in
shutdown mode.
Each CRT screen size has its own safe operating Anode Voltage and
shutdown voltage. Critical Safety components (designated with an
“X” in the component designator) are designed to operate the CRT at
a safe operating Anode voltage and provide proper shutdown thresholds . If replacement of any of these components are deemed necessary, it is important to use original type Zenith replacement components. After replacement is made, confirm proper Anode voltage
using the following procedure.
NOTE: The CB chassis does not have a bleeder resistor to discharge
the Anode voltage. High voltage can remain on the CRT
Anode long after power is turned off. Before removing the
CRT anode connection, turn off and unplug the television,
then discharge the CRT Anode to DAG ground.
When the shutdown circuit is operating, the microcontroller will
avoid that the TV is turned on again unless the microcontroller has
been restarted by disconnecting the TV from the AC line.
Equipment required:
a) Video Generator.
b) HV DC meter (0 to 40 KV, high Z).
c) External variable power supply (0V to 200 VDC @ 5Amps minimum).
Measurement of the CRT Anode voltage must be performed using a
high impedance high voltage meter, with no visible raster on the
screen, and operating at nominal horizontal scanning frequency.
Connect a strong broadcast signal (or TV signal generator operating
at 15.734kHz horizontal scanning rate) to the RF input.
d) 1 Giga ohm, 5%, 2W film resistor.
Note: The external power supply may require a diode for blocking
voltage from the chassis power supply to the external power
supply. The diode should be connected between the positive
output of the external power and B+ of the chassis. The
cathode should be facing the B+ of the chassis. The
recommended diode is Part No. 103-00339-04A (400 V of
VRRM @ 3 Amps of average rectified forward current).
After discharging the CRT, connect a high impedance high voltage
meter to the CRT anode. Turn the television “on” and confirm a good
signal is being displayed . Reduce Brightness and Contrast settings
until the picture is well extinguished.
SHUTDOWN SAFETY CIRCUIT
FROM SWEEP TRANSFORMER
RX3211
1
+9VSW
470 pfd
CX3002
5.6K
RX3005
1.5K
RX3003
D2205
R2224M
8.2K
R2222M
4.7K
FROM FLYBACK
PULSE
PROV
C2215M
PROV
C2214M
0.1 / 25v
C2241M
PROV
R2223M
DX3002
CX3203
47uf
RX3007M
8.2K
PROV
RX3006
PROV
RX3004
QX3002
ZDX3400
RX3002M
33K
VIDEO PROCESSOR
HP / XRAYPOT
RX3001M
10K
QX3001
CX3001M
0.01
IC2200
CB-i
DX3001
Power Supply
Introduction
The CB chassis is a cold chassis designed to support 27”, 32”, and 36” receivers. Its power supply
features a controlled turn-on MOSFET gate driver circuit, direct B+ regulation, thermal protection circuitry,
over-current protection (OCP), over-voltage protection (OVP), over-load protection, provision for future
universal power input (85VAC – 265VAC), and software controlled degaussing.
As with many SMPS circuits, this one activates as soon as it is connected to AC line current via plug
connector 3R8. Depending on the screen size, the CB can draw anywhere from 125 to 140 watts from the
line supply. AC operating tolerances range between 90 Vrms and 135 Vrms. Note that while most of the
functional portion of the CB chassis is considered to have a cold ground, the rectifier and primary side of the
switch-mode power supply have a hot ground.
Switch-Mode Power Supply Primary Side
FX3401, a 4 amp/250 volt fast-blow fuse, protects the CB chassis from AC line surges. EX3401, the
spark gap, also provides some protection for the set. Incoming AC passes the fuse and is filtered by
LX3401, CX3401, and CX3402. The switch-mode power supply (SMPS) uses a fairly standard bridge
rectifier arrangement to develop raw B+, the voltage that runs the SMPS and ultimately the entire television
set. DX3400 is the packaged bridge used in 32” and 36” sets. The 27” sets use discrete diodes DX3401,
3402, 3403, and 3404. Rectifier output (raw B+) will be somewhere between 127.3 and 190.9VDC.
This VDC is smoothed by and can be measured across CX3407.
To Degaussing
Circuit
B+ VDC
FX3401
CX3404
LX3401
3R8
DX3401
DX3402
C3403
DX3400
EX3401
CX3401
CX3402
DX3403
DX3404
RX3401
CX3405
CX3406
CX3407
RX3400
CX3400
To SM Regulator
<<Figure CB-1>>
ICX3412 is the switch-mode regulator IC used to develop the numerous individual power supplies off the
secondary side of TX3401, the chopper transformer. The same chopper is used in all three of the CB sizes.
This transformer isolates the hot portion of the chassis from the cold portion. Raw B+ feeds into pin 18 of
the chopper. The other end of this coil, pin 11, connects with pin 3 of ICX3412. Pin 3 is the drain of the
internal MOSFET that drives the chopper transformer, while pin 2 serves as the MOSFET source.
ICX3412 functions when the voltage on pin 4 reaches +16 volts DC. This voltage is developed on
CX3410. As it starts, the regulator pulls nearly 20mA of current from CX3410, causing its voltage to
CB-1
CB CIRCUIT DESCRIPTIONS
briefly drop. However, as the regulator begins to operate, it drives the chopper, and power derived from
pin 13 of the transformer is drawn through DX3407 to maintain the voltage on CX3410. Overload and
over-voltage protection are both internal to the regulator IC, and sensed through pin 4. Should either of
these conditions occur, and latch will deactivate the oscillator inside ICX3412, thus eliminating any power
supplied by the chopper.
To Rectifier Ckt
ICX3412
5
4
3
2
1
TX3401
C3413
PROV
B+VDC
DX3408
PROV
RX3416
CX3411
RX3415
PROV
18
LX3410
RX3405
LX3417
PROV
CX3412
LX3402
RX3403
CX3409
RX3406
DX3406
CX3418
PROV
13
DX3407
RX3407
Secondary
Side, SMPS
11
RX3404
CX3410
CX3408
16
ICX3403
4
1
3
2
To Secondary
Feedback Ckt.
<<Figure CB-2>>
Pin 1 of the regulator IC allows feedback input for voltage regulation. Control voltage is supplied to this pin
via ICX3403, an opto-isolator that receives output information from the secondary side of the chopper,
particularly from the regulated B+. This feedback is accomplished by the programmable reference device,
ICX3406. The output from this IC is fed to the opto-isolator, which then communicates this signal back to
the switch mode regulator circuit. The output voltage error derived from ICX3403 puts a DC bias across
RX3405 and a drain current ramp on RX3403. The net effect of both the output voltage error and drain
ICX3412
221-00060-03
4
Vin
DRV Bias
UVLO
OVP
Bias
TSD
Latch
OCP/FB Comp
DRV
Oscillator
1
OCP/FB
INH Comp
3
Drain
GND
Source
5
2
<<Figure CB-3>>
CB-2
Power Supply
current ramp is input into pin 1 of ICX3412. This signal is then used to determine how regulation shall
occur as described below. OCP is also sensed using this pin. To prevent a false over-current detection at
startup however, a constant current sink has been included in the regulator. This measure is necessary due
to a current spike that often occurs at startup due to primary capacitance discharge.
The switch-mode regulator makes use of the resonant frequency set up by the chopper transformer and
CX3408. This resonant frequency as well as the internal oscillator determines the nature of the MOSFET’s
switching. Hence, the term quasi-resonant may be applied to this regulator. Regardless of the terminology
used, the IC regulates voltage based on the following simple rule: duty cycle on-time reduces as voltage
rises, while duty cycle off-time reduces as load rises. In this manner, correct voltage is maintained at the
chopper transformer. The regulator’s fundamental switching frequency is 20 kHz, but when the receiver is
switched on, the regulator will operate as high as 100 kHz.
Switch-Mode Power Supply Secondary Side
The secondary side of TX3401 makes use of four separate windings, each with its own half-wave rectifier,
to develop the various voltages required by the television set. As a result there are four primary stand-by
voltages (VSB): B+ (typically +130 volts), +12VSB, +15VSB, and +22VSB. The +15 and +22VSB are
each protected by 3A/250V, slow-blow fuses, FX3402 and 3403. The B+ line has sufficient protection
from the switch mode regulator. RX3423 is a fusible resistor that protects the +12VSB line.
+22VSB
C3423
DX3418
9-2104
9-2105
9-2106
ONLY
PDD
LX3405
+15VSB
LX3404
D3419
FX3403
C3422
IN
RX3417
1
3
OUT
R3425M
C3421
CX3428
Q3405
CX3430
C3429
D3416
D3417
CX3424
6
W3405
FX3402
L3409
8
+12VSB
5
LX3415
Primary
Side, SMPS
R3426
2
C3435
3
+9VSB
ICX3401
L3414
D3411
D3409
7
+5VGEM
ICX3402
L3406
IN
RX3423
1
3
+5VPiP
+9VSW
W3404
L3412
OUT
2
CX3427
C3425
9
+9VSWF
C3426
LX3416
PROV
+9VIF
C3419
1
W3403
LX3403
CX3432
PROV
4
TX3401
B+
D3410
+5VTUNE
+5VSBM
+15VSB
L3407
CX3436
Q3402
R3418M
+15VSB
R3412M
To Primary
Feedback Ckt.
ICX3403
4
RX3409
CX3420
RX3427
1
3
+15VSW
L3408
Aud
GND
ICX3404
1
C
CX3416
R
RX3428
+33VSB
B+
ICX3405
RX3408
2
ICX3406
+12VSW
PROV
2
CX3414
PROV
Q3404
B+
CX3431
Power Control
Pin 32, IC6000
IN
3
1
3
RX3413
OUT
2
C3433
B+
-14AUD
-14VDC
A
4W9
CX3417
PROV
C3434
L3410
R3410
CX3415
RX3421
1
+15VSW
+14AUD
+14VDC
2
L3411
R3411
3
4
IQB32B44W
IQB36B44W
ONLY
±14 Volts DC
from Flyback
<<Figure CB-4>>
CB-3
CB CIRCUIT DESCRIPTIONS
The B+ provides power for deflection via the horizontal output transistor (HOT), QX3204, and for the
tertiary voltages that come from the flyback transformer, TX3204. It also develops the +33VSB for the
tuner through RX3413. The +12VSB is regulated down to +5VSB by ICX3402. This +5 volt source
powers the microprocessor and EEPROM (IC6000 and IC6001 respectively), the Gemstar® board, the
PiP board, and the tuner. The +15VSB is used as is to power sweep correction, horizontal drive amplification, and the ABL circuitry. It is also regulated by ICX3401 for +9V and by ICX3405 for +12VSW. Both
of these voltages are used as various video and IF supplies. The +22VSB is used to power the audio
amplifier.
Two other voltages should be named here, although they are developed from the sweep transformer,
TX3204. Namely the + and – 14VDC pass through the secondary of the switch mode power supply
section. These become the +/- 14AUD volts that power the variable audio output amplifier when they pass
the series resistor and inductor arrangement shown on the schematic.
Some of the above voltages are switched on when the television powers up, rather than when it is just
plugged in. These include +9VSW, +9VIF (some models), +9VSWF, +15VSW, and +12VSW. These
are switched upon receiving a power on DC level from pin 32 of the microprocessor, IC6000. This
switches Q3402, which in turn activates both Q3405 and Q3404.
Degaussing Control
Degaussing is software-controlled by a signal from IC6000. When the receiver is switched on, pin 33 emits
a 760 ms signal that closes the degaussing relay, KX3401, via Q3403. This allows a brief moment of AC
current to magnetize the degaussing coil before the thermistor, THX3415, limits the coil’s power.
<<Figure CB-5>>
3T8 -- To
Degaussing
Coil
+15VSB
Degaussing
Control, Pin 33,
IC6000
KX3401
2
R3419
DX3405
THX3415
Q3403
1
Filtered
AC Line
Part Location
ICX3401
ICX3402
ICX3403
ICX3405
ICX3406
ICX3412
TX3401
Part #
F-52403
F-53046
162-00028-01
221-00167-05A
221-00265-03A
F-53857
095-04576
<<Table CB-1>>
CB-4
Notes
All Models
All Models
All Models
All Models
All Models
All Models
All Models
Microprocessor Control
Introduction
The CB chassis employs IC6000 as its microcontroller. All end user and servicer controls are accessed
using this IC. While most of its functions will be described in terms of how they are used by other devices in
the receiver, a number of facts concerning the microprocessor and its input devices will now be presented.
The microprocessor’s job is to communicate control instructions and feedback information to and from
various other processors and input devices in the set. These include the video, audio, PiP, Gemstar®, audio
& video switch ICs, the tuners, the EEPROM, the keyboard and IR detector, and the reset IC. Some of
these use a direct connection via either switch, variable pulse, or DC level for communication. Others rely
on the I2C bus, also known as serial clock and data bus. IC6000 provides 2 sets of clock and data lines.
The first set is pins 37 and 39, and the second is on pins 36 and 38.
Input Devices
The IR detector demodulates pulses from the 40 kHz modulated carrier and sends the pulses to pin 15 of
the microprocessor. There a special algorithm interprets the pulses as the various commands they represent.
The keyboard is only slightly more complicated in its operation external to IC6000. It works by varying
voltage on only two input pins (7 and 8) using resistor networks. A/D converters inside the micro interpret
the different voltages. Because voltage detection is used rather than active keyboard scanning, keyboard
radiation is not a problem, but maintaining a +5VSB to within ±4% is critical. Both keyboard and IR
information enter the CB chassis through connector 2K6.
Microcontroller
VDD is provided to pin 27 of the microprocessor from the +5VSBF supply. While this voltage is relatively
low, IC6000 is fairly demanding in terms of current. This same voltage powers the keyboard and IR
detector. The +5VSBF is also used as analog VDD and enters the micro at pin 18.
IC6002 serves as a reset IC for the main microprocessor. Note that it comes in a transistor type package.
It accurately resets the micro after a power failure is detected. Pin 30 is the reset signal input for IC6000.
The micro enters reset state after detecting a low on pin 30 of 2µS or more.
When the micro receives a power on signal from either the keyboard or the remote, the degaussing control
pin 33 turns on the degaussing circuit for 760ms. At the same time a constant voltage level from pin 32
turns on the switched voltages in the power supply.
Horizontal and vertical synchronization pulses are fed into pins 1 and 2. These provide the microprocessor
the current sweep location of the beam, which is necessary to correctly interrupt main video for various
types of on-screen display (OSD). Neither of these sync pulses come directly from the IC2200 where they
are first produced. Horizontal sync is actually fed back from the sweep transformer on the flyback pulse
line. Vertical ramp signal coming from pin 5 of IC2200 feeds the base of Q6002. Sync is produced on the
collector and fed to the vertical amplifier and through R6006M to the V-Sync pin of the micro. OSD or
CC (closed captions) are sent as processed RGB (red, green, & blue) from pins 50, 51, and 52. At those
times it is necessary to blank out part of the main video, a fast-blank (FB) pulse is sent to the video procesCB-5
CB CIRCUIT DESCRIPTIONS
sor from pin 49 along with the processed RGB. An exception to this occurs when Gemstar® is displayed.
Under that circumstance, the fast-blanking pulse without RGB is sent to the video processor via the
Gemstar® board.
V-Sync
C6042M
+5VSBF
R6007M
R6005M
R6006M
C6041M
R6008M
V-Ramp
Flyback
R6004
Q6002
C6026M
R6003M
Q6004
+5VSBF
C6001M
C6059M
C6043M
R6001M
+5VSBF
D6002
R6069M
R6070M
Q6001
IC6000
R6002M
1 HSYNC
R6009M
R6012M
C6060M
R6052M
C6061M
C6058M
R6051
SD2
SD
AFC-Main
R6013
R6015M
R6016M
R6010
AFC2
R6063
R6064
R 52
2 VSYNC
G 51
3 AFC
B 50
4 N/C
FB 49
5 SD2
PiP-BRIGHT 48
6 SD
N/C 47
7 KEY1
N/C 46
8 KEY2
N/C 45
9 AFC2
AUD-SWAP 44
10 Y/C1-SENSE
N/C 43
11 Y/C2-SENSE
GM-RESET 42
12 Y/CF-SENSE YUV/SWITCH 41
13 CRT-PROT
R6027
C6034M
R6014M
C6022M
R6011M
C6004M
R6017M
C6044
C6002M
C6040M
L6007
C6007M
C6009
SCL2 38
16 N/C
SDA1 37
SDA2 36
R6033M
N/C 34
20 RVCO
DEG-CTL 33
21 VHOLD
POWER 32
22 CVIN
N/C 31
23 CNVSS
R6080
C6036M
IDENT 35
19 HLF
R6032M
C6005M
15 IR DET
18 AVDD
R6031M
C6006
SCL1 39
17 N/C
R6030
D6003
C6037
Composite Video
CRT-Protect
Mute
Y/C1-Sense
Y/C2-Sense
Y/C-Front-Sense
H/T 40
14 MUTE
+5VSB
24 XIN
C6008M
L6005
RESET 30
OSC-OUT 29
25 XOUT
OSC-IN 28
26 VSS
CRY6001
C6003M
VDD 27
+5VSBF
+5VSBM
R6034M
C6035
PROV
L6004
L6001
C6010M
1 2 3 4 5
2K6
EXTERNAL KEYBOARD
C6011M
C6013
C6012M
<<Figure CB-6>>
The CB chassis features a halftone function that dims video surrounding OSD. This halftone circuit is
described in the video section, but is controlled by a DC level from pin 40.
Closed captioning display is accomplished in the microprocessor by use of the composite video into pin 22.
Here a data slicer extracts the caption information and outputs it to the RGB pins when captioning is requested by the user. Note that when OSD needs to be on the screen, such as after a channel change or
during a volume change, the OSD will have priority, and CC will mute until OSD turns off.
Pins 5 and 6 are signal detection pins. When the either of the chassis’ two tuners detects a bona-fide signal
to the video processor, it separates horizontal sync signal from the IF and sends it to this portion of the
microprocessor. It can then be used to determine if a certain channel is carrying a valid active broadcast.
Automatic frequency correction (AFC) is sent to the microprocessor via pin 3 and pin 9 (for the second
tuner IF). The DC level on either pin tells the microprocessor if it needs to communicate an adjustment to
CB-6
Microprocessor Control
the corresponding tuner to allow for clearer channel reception. The ideal voltage level here should be
between +2.25 and +2.5 volts.
R-Micro
G-Micro
B-Micro
FB-Micro
C6033M
C6025M
R6081M
C6024M
C6023M
R6024M
C6065M
C6091M
R6088M
C6067M
Halftone
IC6000
1 HSYNC
R 52
2 VSYNC
G 51
3 AFC
B 50
4 N/C
FB 49
5 SD2
PiP-BRIGHT 48
Q6003
R6023M
R6061M
PROV
C6038M
C6063M
N/C 47
7 KEY1
N/C 46
8 KEY2
C6054M
N/C 45
R6058M
N/C 43
11 Y/C2-SENSE
GM-RESET 42
C6057M
D6004
SCL1 39
15 IR DET
SCL2 38
16 N/C
SDA1 37
R6071M
PROV
FB-PiP
PROV
H/T 40
14 MUTE
IQB32B44W
IQB36B44W
ONLY
3
PiP-Brightness
Aud-Swap
GM-Reset
YUV-Switch
12 Y/CF-SENSE YUV/SWITCH 41
13 CRT-PROT
1
2
C6055M
AUD-SWAP 44
10 Y/C1-SENSE
4Q9
R6062M
PROV
R6040M
6 SD
9 AFC2
C6046M
J6001M
R6068
C6039M
C6068M
C6052M
C6062M
C6053M
SDA2 36
17 N/C
18 AVDD
19 HLF
IDENT 35
N/C 34
20 RVCO
DEG-CTL 33
21 VHOLD
POWER 32
22 CVIN
Deg-Ctl
Power-Ctl
Power-Fail
N/C 31
23 CNVSS
24 XIN
RESET 30
C6018M C6045M C6046M
OSC-OUT 29
25 XOUT
26 VSS
L6002
OSC-IN 28
VDD 27
CRY6002
PROV
R6035M
C6016
R6060M
C6056M D6001
C6015M
+5VSBF
+5VSBM
C6014M
R6037M
R6059M
IC6002
L6001
OUT
C6013
C6017
VCC
C6012M
GND
<<Figure CB-7>>
IC6000 provides CRT-protection for the set through pin 13. Operation of this shutdown depends on a DC
level from the CRT protection circuit off the vertical amplifier circuit. Should the vertical IC2100 fail, the
DC level will no longer be present. In this situation, the CRT-protection latch will shut the receiver down
three seconds after detecting the failure. This circuit will prevent the CRT from burning a horizontal phosphor line in the center of the screen or, worse yet, cutting the yoke end of the tube off completely.
The remainder of the I/O pins on IC6000 are briefly described here. Where necessary, a more detailed
description will be provided in the circuit descriptions to which they relate. Pins 10, 11, and 12 are used as
S-Video (Y/C) detection for the two Y/C jacks on the back and the Y/C jack on the front (where available). Pin 48 emits a varying DC level that changes the bias on Q2211, effecting the PiP brightness of the
RGB input to IC2200. Audio swap is accomplished by pin 44, which varies a DC level to a transistor array
in the IF section. This array allows the audio signal being heard by the user to be switched between the
primary and secondary IF. Pin 42 controls the Gemstar® module’s reset function. Pin 41, the YUV-SW
varies a DC level on pin 36 of IC2200 to make it switch main video between separated luma and chroma
CB-7
CB CIRCUIT DESCRIPTIONS
signals entering IC2200 at pins 4 and 2 respectively and component video entering at pins 37 through 39.
Note here that component video cannot be used as PiP. Lastly, pin 14 of IC6000 switches a DC level to
alter the mute state of the audio amplifier.
Memory
The EEPROM, IC6001, is a small but vital part of the CB receiver. This 512 byte memory chip is responsible for storing servicer adjustments, channel information, and user settings, even when power is removed
from the set. This information is transferred on the clock and data lines from the micro into pins 5 and 6.
The EEPROM is powered by the +5VSBF source at pin 8.
Clock & Data
for IF, Video
and Audio
R6047M
+5VSBF
R6046M
R6045M
DATA2
CLOCK2
4G9
R6048M
IC6001
4
5
3
6
2
7
1
8
R6050M
1
R6049
2
3
4
5
+5VSBF
R6044M
R6043
R6042M
R6041
R6039M
C6021M
C6050M
C6049M
C6048M
C6047M
R6072
L6003
C6020
39
CLOCK1
38
CLOCK2
37
DATA1
36
DATA2
35
IDENT
<<Figure CB-8>>
IC Location
Part #
Notes
IC6000
221-01388
All Models
IC6001
221-00745-05 All Models
IC6002
221-01177A All Models
<<Table CB-2>>
CB-8
C6019M
(IC6000)
IF Receiver
Introduction
The CB chassis utilizes two tuners in order to provide PiP without requiring a second external source. This
is with the provision that the receiver’s antenna input is receiving multi-channel input. For example, a cable
decoder box usually only provides a single channel input. Although the television possesses two tuners,
each is receiving an identical single channel, so a second external source would have to be used here if the
user desires his PiP to be different from the main screen. On the other hand, a standard cable input or even
a regular antenna provides multiple channels that each tuner can demodulate individually.
The IF (intermediate frequency) section can be broken up into a half for each tuner. Those part designations numbered from 1200 through 1249 relate to the primary tuner, WT1200. Part designations from
1250 to 1289 apply to the secondary tuner, WT1250.
Tuner
For the most part, each tuner is fairly identical to the other as it relates to the rest of the chassis. Each
corresponds respectively to IF IC1200 and IC1250 (IFPs or IF processors), which are also identical. IF
R1217M
R1288M
C1222M
R1226M
C1214
L1204
TP1205
R1202
AGC
Delay
+9VSW
R1203M
2 FM-DET
1ST-SIF-AGC 23
3 IF-AGC2
SIF-OUT 22
8
2
7
5 IF-IN1
3
6
6 IF-IN2
4
5
C1205M
C1201M
C1221M
PROV
EQ-IN 19
APC-FILTER 18
8 SIF-IN1
VIDEO-OUT1 17
9 VCC
L1203
TP1207
C1213
L1200
C1204
R1204
R1201M
L1201
C1207M
U1201
R1209M
VCO2 16
10 RF-AGC-OUT
C1203M
R1211M
R1212M
C1212M
C1211M
C1202M
W1200
PROV
R1216M
EQ-FILTER 20
7 GND
R1213M
C1214M
4 RF-AGC-ADJ VIDEO-OUT2 21
1
U1200
IF-Video
Main
R1214
Q1200
R1224M
C1220M
+9VSW
SIF-IN2 24
C1215M
R1223M
C1219M
C1200M
R1219M
PROV
IC1200
1 DET-OUT
C1290
R1225M
U1202
R1222M
CR1200
11 AFT1
AFT-OUT 14
12 AFT2
IF-AGC1 13
+9VSW
R1207M
R1206
TP1206
AFC
C1210M
R1218M
TP1200
L1202
VCO
VCO1 15
+5VSB
R1208M
C1208
C1206M
AFC-Main
C1209
R1210M
R1241M
R1205M
+33VSW
R1290M
SD-Main
+9VSW
R1246M
+5VTune
R1291M
Q1290
R1299
PROV
ZD1230
10
C1230
C1242
9
C1231M
C1294
R1292M
C1232
Q1240
R1244M
Q1293
R1293M
C1241M
11
8
C1233M
R1243M
7
PROV
C1243M
R1242M
6
R1295M
J1201M
5
C1234 C1235M
Comp-Aud
Q1291
R1298M
PROV
PROV
4
Q1241
C1244M
R1240M
R1245M
C1240
R1294M
3
R1296M
TP1202
R1230M
TP1201
2
R1231M
Q1292
Audio-Swap
R1297M
SDA
SCL
1
C1293M
C1292
Comp-Aud2
+9VFil
+9VSB
L2901
To Main
Tuner
C1236
R1289M
C1237M C1238M
PROV
PROV
C2935
WT1200
Luma-SD
To 2nd
Tuner
Antenna
Input
C2936M
Splitter
Main Tuner
Main-Tuner
<<Figure CB-9>>
CB-9
CB CIRCUIT DESCRIPTIONS
comes from pin 11 of the tuner, is filtered, and is fed into pins 5 and 6 of the IFP. AGC (automatic gain
control) voltage is applied to tuner’s pin 1 from pin 10 of the IFP. The +33VSB tuning voltage is applied to
pin 9, while the +5VTune processing voltage is on pin 7. Clock and data lines from IC6000 communicate
with the tuner on pins 4 and 5. In some receivers, the secondary tuners use the +9VIF at pin 6.
IF Processing
Each IFP is powered by the +9VSW on pin 9. After IF is received at pins 5 and 6, sound IF is separated
from picture IF emitted from pin 17. It reenters the IFP through pin 24 and finally exits through pin 1 as a
composite audio signal. Composite audio from each IFP enters a switching transistor array with part
designations 1290 through 1299. The audio-swap line from the microprocessor controls Q1292. This
transistor switches the rest of the array between composite audio from either the primary or secondary
tuner.
R1257M
C1259
U1253
R1256M
CR1250
L1251
Comp-Aud-2
C1261M
C1262M
C1260M
IC1250
1 DET-OUT
R1259M
R1258M
2 FM-DET
1ST-SIF-AGC 23
R1278M
3 IF-AGC2
SIF-OUT 22
U1251
C1264M
1
4
5 IF-IN1
EQ-FILTER 20
2
5
6 IF-IN2
EQ-IN 19
R1261
3
7 GND
APC-FILTER 18
8 SIF-IN1
VIDEO-OUT1 17
R1273M
L1255
TP1254
C1274
9 VCC
C1273M
U1252
VCO2 16
C1272M
10 RF-AGC-OUT
C1267M
C1266
R1263M
R1262M
R1272M
R1271M
C1265M
+9VIF
L1252
IF2-Video
IF-AGC1 13
C1271M
TP1250
R1265M
R1268
TP1255
AFC
C1268M
R1270M
+9VIF
R1267M
AFT-OUT 14
12 AFT2
C1269M
L1254
VCO
VCO1 15
11 AFT1
L1253
Q1251
R1276M
C1277M
4 RF-AGC-ADJ VIDEO-OUT2 21
AGC
Delay
+9VIF
SIF-IN2 24
C1276M
TP1253
R1260M
R1286M
PROV
AFC2
C1285
+5VSBF
R1266M
C1270
R1280M
C1278
R1269M
R1264M
C1263M
+33VSB
SD2
+5VTune
R1284M
11
ZD1250
10
C1256
C1255M
C1279M
R1279M
C1280
9
Q1253
R1283M
8
C1257
C1254M
7
R1282M
C1281M
6
C1258
+9VIF
C1253M
R1281M
J1250M
5
L1250
4
Q1252
C1282M
R1285M
3
PROV
R1251M
TP1252 TP1251
2
R1250M
1
C1250
C1287M C1288M
SDA2
SCL2
PROV
PROV
WT1250
2nd-IF-Tuner
<<Figure CB-10>>
Two variable coils are available with each IF processor for adjusting AFC or VCO. Use caution when
adjusting these, and be certain to mark their initial position in case they need to be adjusted back to their
previous setting. A potentiometer is also available off pin 4 of the IFP. This adjusts the AGC delay inside
the processor.
CB-10
IF Receiver
The remaining outputs of the IF processor are the AFC control to IC6000 from pin 14 and the IF video
signal which passes through the AV-switch (IC2900) as it travels to the comb filter. AFC output voltage
causes the microprocessor to determine any frequency corrections the tuner needs to make for a better
signal. A portion of the luma from the IF-video is separated and filtered for the purposes of signal detection
at pins 5 and 6 of IC6000. From the main video signal, this separation occurs after the comb filter stage,
where composite video exits IC2900 at pin 34. Signal detect information (SD) is then separated from the
luma by transistors Q1240 and 1241 and their surrounding circuitry. For the second video signal, luma is
taken immediately from the IF video signal out of IC1250 and separated by the circuitry including Q1252
and 1253.
Part Location
IC1200
WT1200
IC1250
WT1250
Part #
221-00792
175-02770
221-00792-01
175-02770
Notes
All Models
All Models
All Models
All Models
<<Table CB-3>>
CB-11
CB CIRCUIT DESCRIPTIONS
Jack-Pack
The CB chassis provides multiple means for connecting external sources that supply video and audio signal.
These provisions include two composite video (CV) inputs, two S-Video (Y/C) inputs, component video
(YUV) input, corresponding left and right channel audio inputs for each video input, and, in some models, a
front input jack featuring CV, Y/C, and stereo audio inputs. Additionally, a two-channel variable audio
output is provided. This portion is discussed further in the audio circuit description.
Audio/Video Switch IC
In order to handle the multitude of incoming signals from the jack-pack, as well as the two internal IF
signals, the CB chassis employs an analog audio/video IC2900. This IC is powered at pin 18 by the
+9VSW. While switching is analog, IC2900 is digitally controlled through the I2C (serial clock and data)
bus connection at pins 26 and 27. This data stream communicates both user selections for signal input as
well as microprocessor priority commands. These priority directives may be explained by the following
example.
R2902 Jumper
Y/C2-Sense
C2901
R2901
See Component Video
JackPack Section
ZD2904
ZD2901
R2904
C2902
2 VINE2
LINE4 54 C2934M
VINE4 53
3 RINE2
RINE4 52 C2930M
1 LINE2
R2906
C2903
Video2-In
R2970M
11
C2905M
R2910
12
Aux2-L-In
R2911
23
R2909 Jumper
24
Aux2-R-In
18
R2914 Jumper
7
C2937
R2916
R2921 Jumper
C2906
6
LINE3 51
5 VINE1
VINE3 50
6 RINE1
RINE3 49 C2928M
7 VINS1
YIN1 48
8 LINS1
CLAMP1 47
9 YINS1
VOUT1 46
10 RINS1
LOUT1 45
C2909
R2918
R2922
5
C2910
C2911M
CINS1
YOUT1 44
12 GND1
ROUT1 43
13 VINS2
COUT1 42
14 LINS2
LOUTD 41
15 YINS2
CIN1 40
16 RINS2
ROUTD 39
17 CINS2
18 VCC
4
R2919
Video1-In
10
12
R2912
Aux1-L-In
ZD2905
19 VINS3
VOUT2 36
20 LINS3
21 YINS3
LOUT2 35
YOUT2 34
22 RINS3
ROUT2 33
23 CINS3
COUT2 32
24 GND2
2
25 MUTE
24
R2972M
Aux1-R-In
Q2903
CV-Micro
R2944M
I/O2 29
27 SCL
I/O1 28
R2953M
IF-Video-Main
Y+C/CV-PiP
R2960M
R2958M
R2954M
Q2901
R2937M
R2955M
R2938M
R2939M
Q2904
R2945M
Luma-Main
Luma-SD
R2956M
Jumper
R2957M
Left-SW
Right-SW
Y-Comb
CV-Comb
C2927
R2940
C2926
+9VSW
R2934M
C2938M
Q2902
R2943M
19
R2952M
C2932
O3 31 C2924M
CIN2 30
26 SDA
IF2-Video
C2933
C2925
YIN2 38
CLAMP2 37
+9VSWF
C2931M
C2929M
4 LINE1
C2908M 11
ZD2906
17
Y/C2-In
C2907
R2908
R2907
+9VSW
IC2900
R2969M
R2933M
C2923M
Chroma-Main
R2935M
C2912
R2936M
17
R2971M
7
Y/C1-In
C-Comb
+9VSW
R2930
9
C2922M
C2914
C2921M
R2923
Y/C1-Sense
R2927
ZD2910
R2931M
R2932M
C2915
C2919M
PROV
C2918M
PROV
C2917M
PROV
IQB27B42W
IQB27B44W
IQB36B44W
ONLY
Jumper
R2973M
<<Figure CB-11>>
CB-12
ZD2903
C2916
ZD2903
SDA
SCL
R2928
C2920M
R2926
R2920M
3
R2924
C2913
R2925
8
Y/C-Front-Sense
ZD2908
R2974M
4A8
1
2
3
4
5
6
7
8
9
A/V Switching
Suppose the user has composite video connected to the Video 1 input and S-Video connected to the SVideo 1 input. If the user selects video source 1 in the customer menu, the receiver must choose between
the CV and the Y/C signal. Each Y/C input has a sensor line that feeds the micro. If the micro detects the
presence of Y/C on video 1, IC6000 will direct the A/V switch to use that Y/C signal instead of the CV.
Thus if it is present, Y/C has priority over CV.
IC2900 features three functional input arrays for jack-pack signal. Each array consists of left and right (L/
R) channel audio input, CV input, and Y/C input. Additionally, the A/V switching IC provides another input
for the dual IF-video signals and input for the Y (luma) portion of the component video input as well as its
associated audio. CV, Y, and IF inputs should scope near 1.0Vp-p. Color burst from the Y/C inputs as
well as audio inputs should scope about 300 mVp-p.
For outputs, IC2900 uses pins 39 and 41 for L/R channel external audio. This is fed to IC1400, the audio
processor and is used if the user selects a jackpack source. Pin 41 serves as the PiP video output. PiP
video is sent as a composite video signal. However, if the PiP source is S-Video, IC2900 internally combines the Y and C signals into a CV signal. PiP CV should have a strength of 2.0 Vp-p at pin 41. Main
video is output to the video processor on pins 32 and 34 as chroma (C) and luma (Y), respectively. The
luma signal should be 2.0 Vp-p while chroma is about 600 mVp-p.
Composite or IF video input to the IC cannot be passed to IC2200 as composite video. Rather, the A/V
switch passes CV or IF video via pin 41 through the comb filter section, where it is separated into luma and
chroma and returned to pins 38 and 30 of IC2900. Voltage at pin 41 should be 2.0 Vp-p. The separated
signal is then sent to IC2200 as Y and C along the main video lines. It should be mentioned that pin 34 also
sends the luma signal to IC6000 so that closed captioning (CC) and synchrony information can be extracted
from it.
Part Location
Part #
Notes
DL2400
223-00045 IQB27B42W
IC2400
221-01040 IQB27B44W
IC2900
221-01053 All Models
<<Table CB-4>>
CB-13
CB CIRCUIT DESCRIPTIONS
Component Video
Component video is handled differently than the other jackpack inputs. The CB lacks conversion circuitry
to make component (YUV) signal into CV. For this reason, component video cannot be used for PiP,
which requires CV input, and is furthermore not separated (or combined) into luma and chroma through
IC2900. YUV is directly input to IC2200 at pins 37 through 39. This arrangement necessitates the use of
a YUV switch from the microprocessor to the video IC. With respect to the A/V switch, however, the Y
component is still input to pin 2 and, when in use, is output as composite video to the microprocessor. As
mentioned before, this information is used to obtain CC and video synchrony. Moreover, the U component
must be amplified to an acceptable level to be used by IC2200. Q2906 and 2907 serve this purpose using
the +9VSWF for power.
YUV-In
Cr-In
Cb-In
R-In
L-In
24
13
14
16
15
20
17
21
R2905
C2940
R2947
C2904
R2949
R2903
C2939
1
2
3
Pins 1-3
IC2900
A/V Switch
R2951
R2946
R2948
R2950
Jumper
ZD2907
1
1
2
2
3
3
R2975M
+9VSWF
4
4
2C4
R2967M
Q2907
4C2
R2961M
C2941
CR-In
YUV-In
CB-In
R2976M
R2965M
Q2906
R2963M
C2943
R2968M
C2942
R2964M
R2964M
R2966M
<<Figure CB-12>>
Comb Filtering
CB receivers use either a 1H glass comb filter, DL2400, or a 2H digital comb filter, IC2400. Both separate
composite video into luma and chroma more efficiently than simple chroma traps and band-pass filters. This
allows for video that is relatively free of color and luma distortion in high detail video objects. Comb filters
are better equipped to distinguish color from high-frequency luma, and can thereby reduce the crosstalk
between the two.
For sets using DL2400, CV from IC2900 enters pin 2. Chroma is output to pin 3 while luma exits the filter
at pin 5. Receivers that possess DL2400 still utilize a color trap (R2470M, L2411, and C2471M) and a
band-pass filter (R2463, L2410, and C2442M) to ensure purity of both chroma and luma before it is
returned to the A/V switch.
CB-14
A/V Switching
On sets using the digital comb filter, CV is fed into an A/D converter at pin 5 of IC2400. This IC is powered by the +5VTune at pins 3, 12, 20, and 27. Output for chroma is at pin 23 and for luma is at pin 25.
Both are further cleaned by transistor circuitry that is powered by the +12VSW. Finally, “combed” luma
and chroma are returned to the A/V switch.
+5VTune
L2415
C2449M
C2406M
+12VSW
+12VSW
R2401M
L2402
C2409M
L2412
Q2401
R2400M
C2405M
C2412M
R2403M
R2402M
R2404M
C2413
C2414M
C2407M
+5VTune
C2415M
R2405M
C2446M
R2407M
VSS4 28
2 VSS1
VDD4 27
3 VDD1
VREF1 26
R2448M
4 VREFH
YOUT 25
R2454M
C2452
COUT 23
7 CLAMPC
BIAS3 22
8 TEST1
VSS3 21
9 1/2VDD
C2417M
C2418M
C2419M
C2445
Q2404
R2426M
C2424M
+5VTune
VDD3 20
L2408
R2446M
CORING 19
11 CKIN
1LINE 18
12 VDD2
VENH1 17
13 VSS2
VENH0 16
C2447M
C2455
R2427M
+12VSW
R2416M
R2473M
CBPF 15
14 KILLER
Q2406
Q2405
4
R2409M
10 FILT
R2458M
3
R2408M
R2455M
6
R2406M
6 BIAS1
R2417M
C2423M
BIAS2 24
5 A/DIN
R2449M
2
L2413
FSC
CV-Comb
R2472M
1 VREFL
C2444M
C2443
C2451M
PROV
C2448
IC2400
R2474M
C2453
R2430M
C2461M
R2471M
R2460M
DL2400
C2459
2
+12VSW
5
1
Y-Comb
3
R2470M
+12VSW
R2457M
4
C-Comb
Q2414
R2444M
R2461M
C2450
L2411
Q2413
R2463
R2447M
R2436M
**Note!
Boxed Areas
ONLY for these:
IQB27B42W
IQB32B42W
IQB32B84R
IQB32B86R
IQB36B42W
IQB36B86R
Q2411
C2471M
L2409
2
3
6
4
R2440M
R2445M
R2439M
L2410
C2442M
R2441M
C2439M
**See Note!
<<Figure CB-13>>
CB-15
CB CIRCUIT DESCRIPTIONS
Introduction
The CB chassis video features include two-tuner PiP, comb-filtered video, auto kine bias, half-tone video,
and direct component video input to the video processor. Certain receiver models also include 2H digital
comb filtering, Gemstar’s® Guide Plus, front A/V inputs, and scan velocity modulation.
At the heart of the video circuitry is the NTSC video processor, IC2200. This video IC is powered by the
+9VSWF at pins 33 and 44. Its primary means of communication with the microprocessor is via the serial
clock and data (I2C) bus at pins 34 and 35.
Video Development
The NTSC video IC handles multiple types of video input and processes the output as RGB (red, green,
and blue). Specifically, IC2200 receives luma and chroma (Y/C) information on pins 4 and 2 respectively.
This input generally serves as main screen video. However, the video processor’s main video input can be
switched via pin 36 to use component video (YUV) that is input to pins 37 through 39. Secondary video
(PiP) is input to the video processor as RGB through pins 26, 27, and 28. The PiP daughter board receives
vertical and horizontal sync information and thereby sends fast-blanking (FB) pulses to pin 25 of IC2200
when main video needs to be blanked for PiP. In this sense, PiP has priority over main video. The microprocessor and, where used, the Gemstar® board also send OSD input as RGB to the video processor into
pins 29 through 31 with FB signals from either source entering the video IC at pin 28.
1
2
3
4
5
6
7
8
9
10
GEM1
1
PiPA1
+5VGEM
2
3
4
5
6
7
8
9
10
R2290
B-OSD+GEM
G-OSD+GEM
R-OSD+GEM
FB-OSD+GEM
FB-Micro
B-Micro
G-Micro
R-Micro
FB-PiP
B-PiP
G-PiP
R-PiP
R2291M
R2292M
R2293M
W6001
W6003
W6004
W6002
+5VGEM
+5VSBM
R6090
PROV
R2296M
R2295M
R2294M
GemStar Connectors
& PDD Circuitry
IQB27B44W
IQB32B44W
IQB36B44W
ONLY
Jumpers Used in
Non-GemStar
Module Receivers
Only
PDD
R6090M
L2205
PROV
R6092M
Y+C/CV-PiP
R6091M
Power-Fail
Flyback
V-Sync
IF2-Video
Reset
SCL2
SDA2
IRBLST2
IRBLST1
1
R2297M
PROV
Q6090
C2290
PROV
+9VSWF
+5VPiP
R6094M
C6090
Q6091
VRamp
SDA
SCL
TP5VBK
R6093M
2
3
4
5
6
7
8
9
10
GEM2
PiPB1
1
2
3
4
5
6
7
8
9
10
<<Figure CB-14>>
Before video can be completely processed, it must also receive ABL (automatic brightness limiter) and ACL
(automatic contrast limiter) information. IC2200 receives this at pin 3. Unlike many receivers, the CB uses
a single input to control both ABL and ACL. For simplicity, pin 3 may be referred to as the ABL pin. ABL
is first taken from pin 8 of the flyback transformer, TX3204. The signal is made positive across C2206 by
the voltage divider formed by R2201, R2212, and R2213. If current level in the picture tube penetrates the
CB-16
Video Processing
limiter threshold (1.5 mA for 27”, otherwise 1.6 mA), the corresponding voltage across C2204 triggers the
limiter circuitry internal to IC2200, thus reducing output level (and therefore the contrast and brightness) of
the RGB signal. ABL helps to prevent blooming in the sweep that would otherwise occur as high current
draw lowers the sweep voltage. It also serves to extend the life of the picture tube.
Chroma-Main
Luma-Main
R2285
C2249M
C2247M
L2203
B+
+15VSW
R2205
PROV
R2256
R2268M PROV
R2269M
PROV
PROV
Q2210
PROV
CRY2201
IC2200
C2201
1 APED
XTAL 47
3 ABLIN
R2204M
ABL
C2250
C2206
C2204
R2206M
R2213
4 CVBS1/YIN
L2202
Hand
Inserted
Component
C2235M
TV/C2IN 43
ABLFIL 42
C2210M 9 COMB-YIN
C2236M
C2234
C2237
R2281
PROV
C2233M
CVBS2/Y2IN 41
8 YCLAMP
GND2 40
10 GND1
EB-YIN 39
11 EW
ER-YIN 38
12 REF
EYIN 37
13 VDP
YUV-SW 36
14 VDN
SDA 35
15 VMOUT
VCC1 33
17 SCP
R2IN 32
18 HP/XRAYPROT
G2IN 31
R2282
C2230
R2252M
PROV
R2250
21 IKIN
R1IN 28
22 ROUT
G1IN 27
23 GOUT
B1IN 26
24 BOUT
C2228M
PROV
C2225M
C2229M
PROV
C2224M
C2223M
B2IN 30
YS2/YM 29
CB-In
CR-In
YUV-In
YUV-Switch
R2251
SDA
SCL
C2232M
C2231M
SCL 34
16 REG
19 HD-OUT
Pins 21-24
Refer to RGB
Output Ckt
C2239
C2238M
VCC2 44
6 MONOUT
20 AFCFIL
R2253M
APCFIL 45
C2208M 7 COMB-CIN
C2209M
R2255M
FSCOUT 46
5 VTIM
R2202
R2254M
NC 48
2 C1IN
R2212
FSC
IQB32B44W
IQB36B44W
IQB27B44W
ONLY
R2286M
R2267M
PROV
Q2208
C2240M
C2248M
C2244
PROV
R2201
R2216
PROV
+9VSW F
IQB27B42W IQB32B86R
IQB32B42W IQB36B42W
IQB32B84R IQB36B86R
ONLY
L2204
R2284M
R2283
R2271M
R-OSD+GEM
G-OSD+GEM
B-OSD+GEM
FB-OSD+GEM
C2222M
YS1 25
R2261M PROV
R-PiP
C2216M
D2211
D2212
C2219M
+9VSW F
R2262M
C2220M
D2213
R2242
R2263M
PROV
PROV
G-PiP
B-PiP
FB-PiP
L2201
R2203M
C2217
+9VSW F
C2241
C2240
R2287
R2279M
R2266M
PROV
R2265M
PROV
R2264M
PROV
PROV
Q2211
R2280M
C2245
R2278M
PiP-Brightness
<<Figure CB-15>>
Another factor involved in determining the RGB outputs is the AKB (automatic kine bias) circuit which
feeds into IC2200’s pin 21. This signal is derived from the CRT circuitry. It uses feedback information
developed by three scan lines of video, one per color, in the over-scanned area above the video image. The
DC level returned is compared with an internal reference voltage that is determined in the service menu
settings for optimum black levels. RGB color is adjusted accordingly and finally output on pins 22 through
24 of the video IC.
IC Location
Part #
Notes
IC2200
221-01394 All Models
<<Table CB-5>>
CB-17
CB CIRCUIT DESCRIPTIONS
Before this processed video is pre-driven by transistors Q2205, 2206, and 2207, the video signal can be
dimmed by the half-tone circuit. This circuit draws a limited amount of current when Q2209 is switched on
by the half-tone pin 40 of IC6000. The half-tone circuit generates a rectangular area surrounding OSD in
which video is present but shaded.
2C5 Key
+9VSW
1:
2:
3:
4:
5:
6:
7:
+12VSW
Setup
AKB-Sense
GND
R-Out
G-Out
B-Out
VID B+
Q2209
D2214
R2233
C2243M
PROV
Q2205
R-Out
Pin 22
C2251
R2236
Halftone
R2231M
R2259M
R2234M
Q2202
ZD2201
Q2206
R2247M
G-Out
Pin 23
D2204
PROV
IKIN
Pin 21
R2245M
R2258M
J2201M
PROV
R2244M
R2237M
R2243M
Q2201
PROV
+12VSW
Q2207
B-Out
Pin 24
R2245M
R2241M
R2257M
PROV
R2240M
R2260
D2206
1
2
3
4
5
6
7
D2207
D2208
2C5
<<Figure CB-16>>
Video Amplification
After the RGB signal is pre-driven, it is sent to the CRT socket via connector 2C5. This socket board
delivers the filament, focus and G2, and RGB video signals to the picture tube. Besides the AKB circuit, the
CRT socket has an afterglow suppression circuit.
Each color is amplified in its own circuit section on the CRT board. The red amplifier section consists of
those parts designated with 5120 through 5130. Green uses part designations 5140 through 5150 and blue
uses 5160 through 5170. The video signal is cascode-amplified by a dual transistor arrangement for each
color. +235 volts from pin 1 of the 5F2 connector supplies power to the cascode amplifiers.
For example, Q5141 and 5142 amplify green signal. Frequency response is the major concern with regard
to Q5142. By itself, Q5142 would tend to lose gain at higher frequencies. To remedy this problem,
C5141M is added to the series-parallel network on Q5142’s emitter. This capacitor along with R5144M
provide an improved response to higher frequency signals, while the resistor, R5143M, improves lower
frequency response in the cascode amplifier. The resistor network formed here by R5145M and R5143M
affect the black level of the green. Q5141 also helps bandwidth of the cascode amplifier. It reduces
feedback caused by parasitic capacitance in Q5142. Q5141 has a very low feedback capacitance, less
than 3pF, and a nearly 300V collector to emitter breakdown voltage. Its cut-off frequency is about 70
MHz. Its collector passes green signal on to the push-pull coupling amplifier formed by Q5143 and Q5144
and finally to the cathode through CRT1, the actual socket on the picture tube. This example applies to all
three color signals, with their respective components substituted.
CB-18
Video Processing
AKB signal is derived from the collectors of Q5124, 5144, and 5164. These are fed back to the AKB
circuit via pin 5 of the 5C2 connector and processed in the manner described above.
The CRT board also features a setup jumper for optimal G2 adjustment. The purpose for it is to force DC
voltage on the cathodes to be equal to the CRT cut-off voltage (170-190 volts DC with respect to G1).
When jumped, the G2 setup circuitry grounds any incoming video signal. The servicer can then adjust the
G2 pot, located on the flyback transformer, TX3204, until retrace lines just start to appear on the screen.
Going back to the example of the green circuit, current then flows in Q5141, D5142, L5141, and RX5146.
It is at this point that raster is almost cut off. When the jumper is released, the AKB circuit adjusts the color
with the highest CRT cut-off voltage to the G2 setup voltage. The other two colors will be just slightly lower
depending on their cut-off settings in the service menu.
RED
BLUE
RX5166
+235V
RX5126
RX5167
RX5127
RX5170
L5161
RX5147
RX5130
L5121
8
G2
RX5146
9
10
R5106
GREEN
C5103
7
11
6
12
5
W5102
PROV
4
L5141
Q5163
Q5123
Q5143
1
RX5150
CRT1
DAG1
DAG2
R5101 W5101
PROV
RX5168
D5162
L5162
L5122
RX5128
D5122
L5142
RX5148
D5142
R5102
RX5169
PROV
R5171
Jumper
RX5129
PROV
R5173
Jumper
Q5164
RX5149
PROV
R5172
Jumper
Q5124
Q5161
R5105
+235V
5F2
Q5144
Q5121
1
Q5141
C5100
C5123
PROV
C5163
PROV
+235V
2
C5101
C5143
PROV
C5102
PROV
R5103
3
4
R5162M
R5142
+12VSW
R5122M
D5161
+12VSW
+12VSW
R5110
PROV
R5104
D5141
Q5162
Q5142
D5121
C5104
PROV
R5165
Q5101
Q5122
R5145M
R5109
D5101
R5107
R5161M
R5125M
R5141M
C5161M
C5106
C5141M
R5121M
+12VSW
C5121M
R5143M
R5163M
5C2 KEY
R5144M
R5123M
R5164M
R5124M
C5105
C5164
PROV
SETUP
1
L5101
DGND
1
2
3
4
5
6
7
5C2
2
1:
2:
3:
4:
5:
6:
7:
Blue
Green
Red
GND
AKB_Sense
Setup
12VSW
<<Figure CB-17>>
The afterglow suppression circuit is used to prevent any residue light that might otherwise remain on the
screen after shutdown. This circuit takes advantage of the fact that the filter capacitor on the +235V line
takes a relatively long period of time to discharge. The loss of filament voltage at shutdown triggers the
switching of Q5101, which then briefly interrupts the G1’s (pin 5) path to ground. The residue voltage on
CB-19
CB CIRCUIT DESCRIPTIONS
C5101 causes the G1 to become more positive. Since G1 is otherwise considered ground for the CRT, this
action reduces any remaining CRT potential, thus eliminating afterglow. C5101 controls the rise time of this
circuit, while C5106 controls the dead-time on response.
Deflection Processing
IC2200 also supplies deflection signals to drive the sweep section. Vertical drive is supplied in the form of
positive and negative ramp signals on pins 13 and 14 respectively. Simultaneously, a vertical ramp is also
supplied from pin 5 of the video processor. This vertical signal is converted into vertical sync, directly by
the PiP board, and through transistors Q6002 and 6004, which then provide the v-sync to the microprocessor and the Gemstar® board.
IC2200
NC 48
1 APED
2 C1IN
XTAL 47
3 ABLIN
FSCOUT 46
APCFIL 45
4 CVBS1/YIN
V-Ramp
VCC2 44
5 VTIM
TV/C2IN 43
6 MONOUT
7 COMB-CIN
8 YCLAMP
ABLFIL 42
CVBS2/Y2IN 41
GND2 40
9 COMB-YIN
R2214M
E/W
VDP
VDN
R2215M
PROVISIONAL ON
IQB32B44W
+9VSW F
IQB36B44W
ONLY
4X9
R2218
10 GND1
EB-YIN 39
11 EW
ER-YIN 38
12 REF
EYIN 37
13 VDP
YUV-SW 36
14 VDN
SDA 35
SCL 34
15 VMOUT
C2213
Pin 18: Refer to
HV Shutdown Ckt
Q2203
16 REG
VCC1 33
17 SCP
R2IN 32
18 HP/XRAYPROT
G2IN 31
19 HD-OUT
1
2
R2220M
20 AFCFIL
C2212M
C2252M
PROV
R2219M
B2IN 30
YS2/YM 29
21 IKIN
R1IN 28
22 ROUT
G1IN 27
23 GOUT
B1IN 26
24 BOUT
YS1 25
R2225M
H-Drive
+9VSW F
R2226M
+9VSW F
L2201
C2241
C2240
<<Figure CB-18>>
Horizontal drive comes from pin 19 of IC2200. This signal drives the horizontal output transistor (HOT).
The flyback line taps off of the HOT collector to provide feedback to pin 18 of the video processor.
Furthermore, this same flyback signal provides horizontal sync for the PiP, Gemstar®, and, through Q6001,
the microprocessor. Pin 18 of IC2200 also serves the second purpose of protecting the set from high
voltage. While pin 18 normally receives horizontal feedback signal, a high voltage situation will activate
QX3001. The collector of this transistor will then attenuate that signal. If attenuation lowers the signal to
1.0 Vp-p or below, IC2200 will shutdown the CB receiver. Lastly, in terms of horizontal deflection, pin 11
CB-20
Video Processing
supplies an E/W pincushion correction signal to IC3200, an op-amp in the deflection circuitry. This signal is
calculated by IC2200 to correct horizontal deflection that would otherwise give a “pincushion” appearance
due to the geometry of the CRT. IC3200 and its function is further described in the deflection circuit
description. Note that it is only used in 32” and 36” CB receivers. Pincushion correction is wound into the
deflection yoke on the 27” receivers.
Two CB models, the IQB32B44W and the IQB36B44W, feature scan velocity modulation. Two coils
located under the purity magnets on the CRT accomplish scan velocity modulation. These coils are controlled by the scan velocity modulator (SVM) board attached to the back of the CRT near the yoke. The
SVM receives fast-blanking and half-tone information from the microprocessor via the 4Q9 connector and
video information from pin 15 of IC2200 via the 4X9 connector. These signals are processed to generate a
current in the coils. The SVM varies this current to slow beam sweep at color transitions. The effect
produces a sharper video image in the CRT.
Shutdown
DC Level
from QX3001
To Shutdown
Pin 18, IC2200
R2224M
C2241M
Flyback
Pulse
C2215M
PROV
R2222M
C2214M
PROV
D2205
R2223M
PROV
<<Figure CB-19>>
CB-21
CB CIRCUIT DESCRIPTIONS
Introduction
The CB chassis was developed to support CRTs ranging from 27” to 36”. Major component of the deflection circuitry include IC2100, the vertical output IC; QX3203, the HOT (horizontal output transistor);
TX3205, the horizontal drive transformer; and on 32” and 36” sets IC3200, the E/W pincushion correction
amplifier. Of course the yoke, connected at 3Y3, and the flyback (or sweep) transformer, TX3204, are
major components as well.
Horizontal Drive
Horizontal drive (H-drive) enters the drive amplification circuitry through C3219 into the base of Q3201.
This transistor and Q3202 amplify the h-drive using the +15VSW for power. H-drive then passes through
the horizontal drive transformer for final wave shaping and voltage to current conversion. This modified
horizontal signal drives the HOT, QX3203. The HOT switches current flow in the primary winding of the
sweep transformer, TX3204. Regulated B+ is applied at pin 3. Horizontal output also drives the horizontal
scan signal in the yoke. Switching frequency of the HOT is 15.734 kHz.
+15VSW
H-Drive from
Pin 19, IC2200
RX3207
CX3213
PROV
R3203
CX3205
R3204
QX3203
R3205
C3219
H-Output to
Flyback & Yoke
TX3205
C3201
CX3212
C3203
Q3201
1
6
C3206
C3202
5
3
Q3202
4
CX3257
PROV
D3203
C3204
R3201M
DX3202
LX3202
R3202M
CX3258
PROV
Flyback Line
RX3212
<<Figure CB-20>>
Flyback Transformer
TX3204 uses HOT switching to generate high voltage. For this reason, the sweep transformer is often
referred to as the high-voltage (HV) transformer. HV should generally range between 29.4 and 31.2 kV.
The flyback does not, however, exclusively develop high voltage. A number of secondary voltages are
derived here as well. These should not be confused with the secondary voltages off the chopper, TX3401.
The voltages developed off TX3204 are referred to as tertiary voltages in the power supply circuit description.
Pin 2 of the sweep develops the +235V used to drive the cathodes at the CRT socket. This voltage is
rectified and smoothed to DC by DX3201 and CX3208 and then applied to pin 4 of the 2F5 connector.
Most of the secondary voltages are developed as DC in such a manner with the exception of pin 7’s filaCB-22
Deflection Control
ment voltage, which is fed into pin 1 of the 2F5 connector, and pin 8’s ABL signal. For the filament’s part,
since this voltage is needed only to heat the cathodes, it is not necessary that it be a DC voltage. ABL is fed
to the video processor in order to regulate beam current.
ABL
+235V
H-Output
E
GND
8
C2114
G2
FOCUS
-14VDC
DX2105
-14VSW
RX2125
+235 V
CX3208
RX3206
2F5
RX3208
+14VDC
TX3204
C2112
C3209
9
HV
B+
DX3201
1
5
2
7
3
6
+14VSW
4
To Video
3 Output
RX2124
DX2104
2
RX3210
PROV
RX3209
1
RX3217
CX3207A
CX3207
PROV
C2111
+33V
+35V
RX3211
DX3252
RX3216
CX3212
CX3254
To Flyback
Line Circuitry
CX3253
To HV ShutDown Circuit
<<Figure CB-21>>
Pin 6 provides power for the +35V supply previously mentioned. RX3216 drops some of this voltage to
+33VSW, which supplies the tuners. Pins 9 and 4 develop, correspondingly, a positive and negative
14VDC. This ±14 volts powers the audio section. RX2125 and RX2124 serve as fusible resistors for the
±14VSW supply to the vertical amplifier, IC2100.
Part Location
Part #
Notes
IC2100
F-53864
All Models
QX3203
F-53367
All Models
TX3204
095-04438-04 All Models
<<Table CB-6>>
CB-23
CB CIRCUIT DESCRIPTIONS
High Voltage Shutdown
The x-ray protection (high voltage shutdown) circuit uses the current from pin 6. DX3002 and CX3003
convert this current to DC. The resulting voltage is applied to the resistor divider network in the emitter
circuit of QX3002. Voltage applied to the base of this transistor remains constant because of the zener
diode, ZDX3004. If HV reaches 35.7 kV (33.9 kV for 27” sets) DC applied to the emitter of QX3002
will switch the transistor on. The resulting voltage across RX3002M will switch QX3001 on, attenuating
the flyback signal on pin 18 of the video processor. If the signal is reduced to 1 Vp-p or less, IC2200 will
cease production of H-drive and thereby shut down the set.
From Sweep
Transformer
RX3211
To Shutdown
Pin 18, IC2200
DX3002
RX3005
CX3002
RX3006
CX3003
C2241M
C2215M
PROV
RX3004
RX3007
R2224M
Flyback
Pulse
RX3003
QX3002
R2222M
ZDX3004
C2214M
PROV
D2205
R2223M
PROV
QX3001
RX3001M
DX3001
CX3001M
RX3002M
<<Figure CB-22>>
Vertical Amplification
The yoke receives vertical sweep drive from ICX2100, the vertical amplifier. This IC consists of a pumpup stage, a power amplifier, and thermal protection circuitry. The ±14VSW power the IC at pins 1 and 6.
ICX2100
221-1410
6
5
7
Thermal
Protection
Pump-Up
AMP
4
+
3
<<Figure CB-23>>
CB-24
1
2
Deflection Control
Both positive and negative vertical ramp signals are required for operation. IC2200 supplies these to pins 4
and 5 of the amp as non-inverting and inverting input. Pin 3 is an input for output stage VCC. Pin 7 is the
pump-up output. Vertical output comes from pin 2 of the amp to pin 4 of the yoke connector. The other
end of the yoke provides feedback to pin 5 of the vertical amp and to the horizontal pincushion correction
circuit.
+14VSW
-14VSW
D2101
C2103
CX2100
C2104
CX2102
To CRT
Protection
Circuit
CX2101
VDP, Pin
13, IC2200
R2102M
6
4
3
ICX2100
7
Vert-Output
2
R2101M
VDN, Pin
14, IC2200
C2106
5
R2103M
1
RX2105
RX2106
RX2107
C2107
32" & 36"
ONLY
Vert-Parabola
R2104M
CX2105
RX2110
RX2111
RX2114
PROV
<<Figure CB-24>>
The pump-up output from pin 7 feeds the CRT-protection circuitry. This circuitry provides a DC level to
pin 13 of IC6000, the microprocessor. The DC level at that pin should be between 3.6 and 5.1 volts. If
the voltage deviates from this range, the microprocessor will shutdown the set in 3 seconds. IC6000 will
have to be reset before the receiver can be turned on again. The purpose of this circuit is to prevent phosphor burn or worse, the severing of the neck of the CRT. Pump-up current is rectified and smoothed by
D2102 and C2108. R2109M and R2112M divide the resulting voltage before it passes through R2113M
to the micro. D2103 is a clamping diode.
+5VSBF
D2103
From Pin
7, ICX2100
R2108M
D2102
R2109M
C2108
R2113M
To Pin 13,
IC6000
R2112M
<<Figure CB-25>>
CB-25
CB CIRCUIT DESCRIPTIONS
Width and Geometry Correction
East/West pincushion correction is performed by circuitry built into 32” and 36” sets. The windings of the
yokes used in the 27” CB chassis have this correction shaped into their design at assembly. Correction is
necessary on larger sets due to their geometry. As the CRT electron beam approaches the upper and lower
extremes of the screen, its horizontal scan lines sweep a wider length than they do in the middle of the
screen. DX3250, DX3251, CX3216, CX3252 and CX3256 act as a diode modulator circuit to limit
current in the horizontal yoke when the sweep is at the higher and lower edges of the screen. This diode
modulator relies on signals amplified by Q3250 and QX3251, and supplied by both the vertical yoke and
the video processor. Q3250 receives its power from the +35V derived at CX3253 off the flyback.
IC3200 is an op-amp that boosts the signal from IC2200. It is powered by the +15VSW, and provides
not only pin-correction information, but also width control. Varying the DC level on the base of Q3250
alters the overall screen width by changing the current through LX3201, the width coil.
ABL
+15VSW
Vertical
Parabola
R3268
R3267
R3258
DX3203
R3261M
R3263M
C3224
RX3214
C3255
R3262M
E/W
TP3200
R3264M
RX3215
LX3201
R3259
IC3200
1
2
3
LX3262
W3200
+35V
4
C3217
CX3215
8
7
6
R3266M
5
R3257M
W3259
W3202
CX3251
DX3251
LX3203
DX3250
H Yoke
+15VSW
R3253
CX3252
RX3256
CX3216
QX3251
R3251M
Q3250
CX3256
R3252M
R3255M
W3203
H-Output from QX3203
<<Figure CB-26>>
CB-26
CX3218
Audio Development
Audio Processing
The CB chassis uses IC1400 to process audio. This IC features true MTS (Multi-channel Television
Stereo) sound, dbx noise reduction, and SAP (second audio program) processing. Its I2C bus at pins 9 and
10 allows adjustment for volume, balance, tone control, front surround sound, SAP switching, source
selection, and stereo separation. IC1400 is powered by +9VSB at pin 24 and grounded at pins 22 and 11.
CB television receivers make use of at least 2 audio inputs to the audio processor. A third set of inputs is
employed on IQBxxB44W type models for audio boost purposes. A description of this process is below.
The composite audio comes from a switch in the IF section through C1436 into pin 19. This allows selection of composite audio from either the main or the PiP IF source. Refer to the IF circuit description for an
explanation of this switching. IC1400 processes this audio, separating SAP, left, and right audio. The left
and right channels are then output on pins 6 and 7. Alternately, the audio processor can use audio input
from an external source at pins 39 and 40.
Switched
Audio In
C1401M
C1403M
C1406M
C1431M
To Audio
Boost Circuit *
C1409
C1410
48 BASSL1
BASSL2 1
47 BASSR2
TRE-R 2
46 BASSR1
TRE-L 3
45 SURRTC
SURRIN 4
44 TVOUT-L
SURROUT 5
43 TVOUT-R
LSOUT-R 6
42 AUX2-L
LSOUT-L 7
41 AUX2-R
NC 8
40 AUX1-L
SDA 9
39 AUX1-R
C1432
R1409M
R1405M
Clock &
Data Lines
C1415
DGND 11
37 VLDC
SAD 12
C1422
R1407M
R1408M
C1424
NC 15
33 VEOUT
PCINT1 16
32 VETC
PCINT2 17
C1428
COMPIN 19
29 SAPIN
VGR 20
28 SAPOUT
IREF 21
27 NOISETC
R1425M
C1434M
PROV
C1421
C1416
R1406M
25 SUBOUT
C1420
C1418
R1421M
C1436
C1413
R1404M
R1422M
GND 22
SAPTC 23
26 STIN
C1427
C1435M
PROV
PLINT 18
31 VEWGT
30 VE
C1426
To Audio &
External Amps
MAININ 13
34 VCAIN
C1419
C1404M
MAINOUT 14
35 VCATC
C1417
R1402
R1401
SCL 10
38 VLTC
36 VCAWGT
C1414
C1402M
+9VSW
Composite
Audio In From
IF Circuit
C1425
VCC 24
IC1400
C1430
C1433M
* Not used
in all models
<<Figure CB-27>>
All audio input and output pins should meter 4.0 DC volts. Signal at pin 19 should have a strength of 245
mVrms. All other audio inputs and outputs on IC1400 should scope at 490 mVrms. This includes the audio
boost I/O described now.
CB-27
CB CIRCUIT DESCRIPTIONS
Audio Boost
Those sets that have the audio boost feature output audio signal on pins 43 and 44 to IC1401. This IC is
powered by the ±14AUD. It strengthens the audio signal and returns it to pins 41 and 42 of the audio
processor. From here, the boosted signal is output from IC1400 on pins 6 and 7.
R1490M
C1471M
R1471M
1 OUT1
R1491M
OUT4 14
R1472M
R1489M
R1473M
2 -IN1
-IN4 13
3 +IN1
+IN4 12
R1488M
R1487M
C1482M
C1472M
R1474M
+14AUD
4 V+
C1480M
C1484
IC1401
R1486M
V- 11
-14AUD
R1485M
C1479
C1481
C1473
C1478M
C1477M
R1475M
5 +IN2
+IN3 10
6 -IN2
-IN3 9
R1484M
C1474M
R1493M
R1476M
R1483M
42
43
TVOUT-R
IC1400
AUX2-R
R1478M
41
C1475
R1482M
R1479M
7 OUT2
44
AUX2-L
IC1400
TVOUT-L
OUT3 8
C1476M
R1480
R1492M
C1483
R1477M
R1481M
<<Figure CB-28>>
Audio Amplification
CB receivers employ two 8-ohm, 7-Watt speakers. These are driven by IC804, the stereo audio amplifier.
Although the audio amp is capable of driving 10-Watt speakers, the supply voltage has been reduced from
+36 volts DC to +22 volts. Normal gain of this IC is 42 dB. In order to drive the speakers at 5 Watts, a
signal strength of only 50 mVrms is necessary. Such a low strength signal is susceptible to noise interference, so the gain is reduced to 32 dB by negative feedback from the output in order to allow for an increased signal strength of 142 mVrms. R868 and R869 accomplish this reduction for the right channel and
R858 and R859 do so for the left channel. The output level from the amplifier is 425 mVrms. Cut-off
frequency is 14.3 kHz and is determined for right and left channels by C865M and C855M respectively.
IC Location
IC803
IC804
IC1400
IC1401
Part #
Notes
221-00170 All Models
F-53765
All Models
221-01127 All Models
221-00188 IQB27B44W
<<Table CB-7>>
CB-28
Audio Development
The +22VSB is supplied to pin 10. Pins 4, 9, and 12 are grounds for the amp. Pins 5 and 2 input left and
right (L/R) channel audio fed through C851 and C861, which eliminate any DC accompanying the signal.
Pin 3 provides a reference voltage. L/R output comes from pins 7 and 11. Pin 8 is a line that, upon receiving a switching DC level from the micro, mutes the speakers. This occurs when the user selects the speaker
cutoff option.
External Audio Output
External variable monitor output jacks are included on the CB jack-pack. Their signal is provided by
IC803, a dual op-amp that receives L/R from IC1400 into pins 3 and 5. This amp IC is powered by the
±14AUD at pins 8 and 4. Audio output to the variable audio output jacks comes from pins 1 and 7. The
op-amp provides a net gain of 12 dB.
L & R Out
from Pins
6 & 7, IC1400
-14AUD
C823
R823M
+14AUD
C850
6
R869
7
+22VSB
C843
C862
C844M
R868
C842
R861M
R822M
C857
R851M
C856M
C864
R832M
3
IC803
4
5
3
6
2
7
1
8
C832
C861
C822
C851
6
C855M
R862M
11
VREF
5
C865M
10
1
IC804
VCC
+INR
OUTR
MUTE
+INL
2
C863
OUTL
3
GND
GND
4
-INL
R852M
4
GND
9
12
8
C854
7
C852
C833
R863
R826M
9S4
1 -INR
2
R833M
CX841
R836M
C853
To TV
Speakers
R858
R859
R853
R834M
R824M
R835
R870
R825
25
Variable
Monitor
Out-Right
27
Mute
C847
PROV
26
Variable
Monitor
Out-Left
Part of J1,
Jack Pack
<<Figure CB-29>>
CB-29
CB TROUBLESHOOTING
Start
1. No Power
Is AC
connected?
No
Plug receiver
into AC source.
Yes
Does FX3401
conduct?
Replace
ICX3403,
ICX3406 as
necessary.
Replace
FX3401.
No
Yes
Is B+ present at
CX3420?
No
No
Yes
Yes
Is +12VSB
present across
CX3427?
Is pin 3,
ICX3412
switching?
Yes
Check RX3423.
Replace TX3401 if
necessary.
No
Yes
Is +5VSB
present across
C3426?
No
Replace
ICX3402.
Yes
Does pin 32,
IC6000 emit a
DC pulse at
startup?
No
Replace
IC6000.
Yes
Does FX3402
conduct?
No
Replace
FX3402.
Yes
Is +9VSB
present across
C3429?
No
Check +15VSB
supply at CX3428.
Check ICX3401.
Yes
Is +9VSW
present across
CX3436?
Check Q3402 &
Q3405.
No
Yes
Is Horz & Vert
drive present on
pins 13, 14, 19,
IC2200?
Yes
Refer to shutdown
troubleshooting.
CB-30
No
No
Are ICX3406
and ICX3403
OK?
Replace
IC2200.
Check DX3406,
DX3407, CX3410.
Replace ICX3412
if necessary
Flowcharts
2. Shutdown
Start
Does the set
power up for
more than 2
seconds?
No
No
Check
microprocessor
ciruitry.
Yes
Yes
No
Does the Vp-p
level at pin 18,
IC2200 stay
below 1.0 volts?
Check HVshutdown circuit,
sweep
transformer.
Does the set
shutdown after
just 3 seconds?
Yes
Check IC2100 &
CRT protection
circuit.
Is B+ running at a
constant DC
level?
No
Replace
ICX3412.
Yes
CB-31
CB TROUBLESHOOTING
3. No Tuning
Start
Are all tuner
voltages
present? (Refer
to schematics.)
No
Check tuner
power supplies.
Yes
Is IF present at
pin 11, WT1200?
No
Does changing
the tuner fix the
problem?
No
Check IF line.
Replace U1200
if necessary.
Yes
Is IF present at
pins 5, 6,
IC1200?
Yes
Is IF present at
pin 17, IC1200?
This procedure may be
applied to the 2nd tuner
section as well.
CB-32
No
Yes
Refer to No Audio and No
Video Troubleshooting.
Check IC1200
power supplies.
Replace IC1200
if necessary.
No
Check clock and
data lines.
Replace IC6000
if clock & data
lines OK.
Flowcharts
4. No Video
Check TX3204
for high voltage.
Check HOT and
H-drive circuit.
Yes
Yes
Start
Is raster present
on the screen?
No
Is 1.07 kVp-p
signal present on
collector of
HOT?
No
Is regulated B+
present at pin 3
of TX3204?
No
Check Q2901
and +9VSW
source.
No
Check power
supply.
Yes
Is there luma at
pin 4, IC2200?
Yes
Replace IC2200.
No
Is RGB output
present at pins
22 - 24, IC2200?
Yes
Check Q2205,
2206, 2207.
No
Is RGB present
at pins 1, 2, 3,
connector 5C2?
Yes
Remove setup
jumper.
No
Is the SETUP
jumper open?
No
Is luma missing
at pin 34,
IC2900?
Yes
Is composite
video missing at
pin 36, IC2900?
No
Check DL2400
or IC2400 and
comb-filter
circuitry.
Yes
Is there video IF
present at pin
50, IC2900?
No
Check video IF
line, Q1200, pin
21, IC1200
Yes
Replace IC2900.
Yes
Check TX3204.
No
Is +235 VDC
present across
C5100?
Yes
Check G2
adjustment.
CB-33
CB TROUBLESHOOTING
5. No Audio
Start
Is +22VSB
present on pin
10, IC804?
No
Check audio
power supply.
Yes
Does DC level
change at pin 14,
IC6000, when
speaker cut-off is
toggled?
No
Replace IC6000.
Yes
Is L/R channel
audio missing at
pins 2, 5, IC804?
No
Replace IC804.
Yes
Is L/R channel
audio missing at
pins 6, 7,
IC1400?
No
Check L/R
channel lines.
Yes
Is composite
audio missing at
pin 19 of
IC1400?
No
Check IC1400
VCC. If it is
present, replace
IC1400.
Yes
Is composite
audio present at
pin 1, IC1200 (or
IC1250)?
Yes
Check Q1290,
1291, 1292, &
1293. Replace
as necessary.
CB-34
No
Replace IF
processor.