6.9.7 OVERSHOOT ADJUSTMENT PROCEDURE
The
following steps are used to adjust the overshoot of the positioner.
6.9.7.1 Test Configuration
(1)
Prepare the positioner
as
described in Paragraph 6.9.1.
(2)
Set the oscilloscope as follows.
• Set Channel
1 sensitivity to 0.2v per division.
• Con nect Channel 1
X10
test probe
to
TP20.
• Set
Channel 2 sensitivity
to
0.2v per division.
• Connect Channel 2
X10
test probe to
TP2.
• Using a
X10
probe, connect external trigger input
to
TP12 on the Logic PCBA.
• Set sweep rate to 1 msec per division.
• Use normal sync, external trigger mode, and trigger slope negative.
(3)
Set the disk exerciser to perform.a one-track repetitive seek from cylinder
000
to
cylinder
001.
6.9.7.2 Adjustment Procedure
(1)
Select Chopped mode on the oscilloscope.
(2)
Observe waveforms at TP20 (Figure 6-6) and
TP2
(Figure 6-8) while performing
one-track seek.
(3)
While adjusting
R79
for
minimum overshoot (Figure 6-12), ensure that the
positive peak
of
the waveform at TP2 is
>+
4v
and that the negative excursion is
>-2v
(Figure 6-8).
6.9.8 INDEX
TO
QUADRATURE CLOCK RELATIONSHIP
This adjustment is used
to
correctly establish the relationship between the trailing edge
of
the Quadrature Clock (SPQCG) with respect to the trailing edge
of
the Index Logic Signal
(SPTIG)
as
shown in Figure 6-13.
6.9.8.1 Test Configuration -
Step 1
(1)
Set the oscilloscope
as
follows.
• Set
sensitivity
of
both channels to
O.2v
per division.
• Connect Channel 1 test probe to
TP7.
• Connect Channel 2 test probe to TP13.
• Sync internal on Channel 1 , use positive trigger slope.
• Set sweep rate to 1 msec per division.
• Set channel select switch to Chopped mode.
(2)
Set exerciser to operate in the repetitive restore mode.
8300
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