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5.
When the logic chassis speed detection determines that the spindle speed is
adequate, relay K5 energizes.
The contacts of K5 cause the following:
a.
Distribute +40 volts to the read/write logic.
b.
Send a Speed Enable signal to the logic chassis (Figure 4-7).
c.
Remove one of two grounds to SSW4 which is controlling the operating
brush motor (Figure 4-7).
d.
6.
Energize relay K4 (Figure 4-8).
The transferring contacts of K4 cause the following:
a.
Apply an additional +20 volt line to the armature of relay K3 (Figure 4-8).
b.
Connect the power amplifier to the positioner so that the logic may
begin providing motion commands to the positioner (Figure 4-7).
7.
As the disk pack cleaning brushes return from sweeping the disk surfaces,
the brush cycle switch mechanically transfers to the not-in-progress
position.
This removes the remaining ground to SSW4 and disables the
brush motor.
It also signals completion of the brush cycle to the logic
chassis (Figure 4-7).
8.
Completion of the brush cycle allows the start of the First Seek (load heads)
function.
Upon completion of the First Seek operation the unit is ready to
respond to commands from the controller.
Power-Off Sequence
The normal Power-Off sequence begins when the operator panel switch S501 is
pressed so as to extinguish the related indicators.
The progression of the
sequence is as follows:
1.
Press operator panel switch S501 (Figure 4-8).
The -20Y voltage is
switched to cause the following:
a.
Absence of -20Y voltage to SSW1 and SSW2 removes ac voltage to
spindle motor.
b.
Presence of -20Y voltage at spindle hysteresis brake causes rapid
deceleration of disk pack.
c.
Spindle speed enable to logic chassis drops.
This disables read/write
logic and causes the carriage to begin moving in reverse toward a
point where the read/write heads unload.
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