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7901A
e. Connect oscilloscope probe to A-channel amplifier test
point A9TP4 on encoder assembly A9.
f.
Synchronize oscilloscope with Set Cylinder signal at
test point A10TP2 on drive control assembly A10.
g. Adjust A GAIN control A9R5 on encoder assembly A9
so that the position waveform is 12 volts
peak-to-peak.
Note:
The amplitude of the B-channel signal
may vary between tracks. The waveform
should never be less than 10 volts peak-
to-peak during a single track seek. How-
ever, the amplitude may be less than 10
volts peak-to-peak during a multitrack
seek.
h. Center the waveform with A BAL control A9R1 on
encoder assembly A9 until positive and negative excur-
sions are equal.
i.
Program the disc service unit to alternately seek
between cylinder 000 and 202. (Refer to HP 13219A
Disc Service Unit Opera ting and Service Manual.)
j.
Connect the oscilloscope to the ACCESS READY test
point on the disc service unit.
k. Adjust VEL CMND variable resistor on cylinder address
assembly All so that the Access Ready signal is low
(O-volt) for 62 ±1
milliseconds.
I.
Set the DRIVE OPERATION CONTROL switch of the
disc service unit to ACCESS STOP.
m. Set the LOAD switch off and remove disc drive power.
n. Perform the head alignment procedure.
5-42.
HEAD ALIGNMENT.
5-43.
To align the disc drive heads, proceed as follows:
a. Turn on the disc drive power and set the DATA
PROTECT switch to the PROTECT position.
b. Install the alignment cartridge, part no. 1535-0066.
c. Remove disc drive top cover.
d. Set TEST switch Sl on sector cylinder assembly All to
TEST position (toward back of drive).
e. Press the LOAD switch.
f.
Set the disc service unit to allow the disc drive to
alternately seek between cylinders 000 and 128. The
DELAY switch must be on. (Refer to HP 13219A Disc
Service Unit Operating and Service Manual.)
Maintenance
g. Allow the disc drive to operate in this manner for
approximately 25 minutes to stabilize disc drive
temperature.
h. Using the disc service unit, position the carriage to
cylinder 100 and select head O.
i.
Connect the oscilloscope to test point TP1 on read/
write preamplifier assembly A6.
j.
Connect the oscilloscope sync probe to IND test point
All TP3 on sector cylinder assembly All.
k.
Set the RESET DRIVE FAULT switch on the disc
service unit to
ON.
l.
Loosen the locking screws that hold the heads in
place.
(See figure 5-8.)
m. Using the head adjusting tool as shown in figure 5-8,
position the head to minimize amplitude modulation of
the output signal. (See figure 5-9.)
n. Tighten the locking
screw
and ensure that the adjust-
ment has not changed.
o. Perform a seek to cylinder 95 and ensure that the
circumferential adjustment waveform is present. (See
figure 5-10.)
Note:
If the waveform is not present, it is
possible that the head was aligned to
cylinder 105 instead of cylinder 100.
p. Using disc service unit,
select
head 1. (Refer to the HP
13219A Disc Service Unit Operating and Service
Manual.)
q. Perform steps k through n for head 1.
7901-31
Figure 5-8. Head Alignment
5-11
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