6300
6.14.7.2 Adj ustment Procedure
(100
tpi only)
If radial alignment is required, perform the following procedure.
(1)
Set
up oscilloscope as follows.
• Connect oscilloscope vertical input to
TP19
on the Read/Write PCBA.
Use
·TP18
for ground reference.
• Set vertical sensitivity to
20
mv per division and select the input
ac
mode.
• Connect a
X10
test probe from the external trigger input
of
the oscilloscope to
TP2
(Index) on the Logic PCBA.
• Use external trigger and normal sync, ac-coupled on the negative trigger slope.
• Set sweep rate to 5 msec per division.
(2)
Observe the waveforms shown in Figure
6·31
and determine which direction the
heads must
be
moved.
(3)
Locate the two radial positioning screws on the selected head.
(4)
By
loosening one screw and tightening the other, position the selected head until
the waveform
of
Figure
6·31C
is obtained. Then tighten both screws without
disturbing the adjustment.
(5)
Align both heads in the same manner.
(6)
Set exerciser to position the heads to cylinder
073.
(7)
Select head
O.
(8)
Observe waveform at
TP19
and compare
it
to the waveform shown in Figure
6·31.
(9)
Select head 1 and repeat Step
(8).
NOTE
If
a head cannot
be
adjusted to obtain the minimal lobe
pattern, the head may not be flying correctly.
This
condition
can
be caused by either a dirty disk
or
head,
incorrect head load force, or damaged
head(s).
6·64
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