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6 22. 350kHz/370kHz Synthesizer Test
This test checks the circuits in the signal path shown in Figure 6-14. Although the measured
signals pass through many blocks, the circuit extensively tested is the 350kHz/370kHz Syn­
thesizer. A 10MHz reference signal from the rear panel of the -hp- 3325A opt 001 is input to
the 10MHz switching box. A counter measures the frequency at A3TP205 of the +- 25 block
of the 350kHz/370kHz Synthesizer. A 3455A voltmeter is connected to A3TP202. L14 is
switched into both states; the user is asked to check for the correct frequency reading for
each state. The counter is then connected to A3TP200 and the test is repeated. A procedure
for adjusting A3L203 then follows. In the next part of the test, the counter is connected to
the Channel B, Output and the output of the -hp- 3325A opt 001 is connected to the IF Input
of the -hp- 35601 A. Again, the frequency reading of the counter is checked for both states of
L14. The program doesn't take readings from the counter in this test; all readings are user
verified. The results are printed.
Initializing the Test
With the Low Frequency Menu is displayed, press special function key (SFK) Kl to initialize
the test. After initialization, follow the instructions displayed on the computer.
What if the Test Fails?
If the frequency reading at A3TP205 is incorrect, check the following circuits:
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Q200of the -^25 block
Q302 of the 10MHz Output Buffer
the 10MHz Reference Input block
the 10MHz Switching board (A6)
If the frequency reading at A3TP200 is incorrect, check the following circuits:
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the -s- 25 block
the -5- 35 block
the Phase Detector block
the 14MHz VCO block
the Buffer block following the VCO
If the frequency reading was correct at A3TP205 and A3TP200, but is incorrect at the Chan­
nel B Output, then the failure is not in the 350kHz/370kHz Synthesizer. The failure is prob­
ably in one of the following circuits:
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the Mixer Driver
the PM Mixer
the Input Amplifier or the 350kHz Bandpass Filter
the 50kHz LPF, X5 Amplifier, X20 Amplifier, Switchable LPF, the Output Buffer, or
any of the associated switches and drive circuitry.
Refer to Service Group One for schematics, component locators, and circuit descriptions.