6.8.2.2 Test Procedure
(1)
Manually move the positioner carriage slowly, and at a constant rate, back and
forth through its
full stroke, Le., cylinder 000 to cylinder
202
(cylinder
000
to
405
for
200
tpi).
Do
not unload the heads rom the disk.
(2)
Monitor
TP2
on oscilloscope Channel 1 and observe the X +
90
Position
Quadrature waveform shown in Figure 6-4 as the positioner is being moved. The
peak-to-peak
voltage observed throughout the
full
stroke
of
the positioner must
fall
within
the acceptable
limits
listed in Step (3). If the acceptable
limits
are
exceedea perform the adjustment procedure detailed in Paragraph 6.8.2.3.
(3)
Acceptable limits:
•
13.2v (maximum) peak-to-peak
• 10.8v (minimum) peak-to-peak
6.8.2.3 Adjustment Procedure
(1)
Adjust potentiometer
R226
(X
+
90
Gain) to attain a 12v peak-to-peak sine wave at
TP2
on the oscilloscope screen while the positioner carriage is being slowly
moved back and forth through its full stroke by hand.
NOTE
Clockwise rotation
of
R226
will
increase amplitude.
(2)
Adjust potentiometer
R79
(X
+
90
Balance)
to
center the sine wave equally about
ground.
If required, reposition the ground-referenced sweep trace to the center
graticule line.
(3)
Perform X + 0 and X +
90
Signal Polarity and Quadrature check detailed in
Paragraph 6.8.3.
6.8.3 X
+ 0 AND X
+90
SIGNAL POLARITY AND QUADRATURE CHECK
The following procedure will verify the correct polarity
of
the X + 0 and X +
90
signals and
their correct phase relationship.
6.8.3.1 Test Configuration
(1)
Prepare the positioner as described in Paragraph 6.7.1.
(2)
Set the oscilloscope
to
the chopped mode.
(3)
Connect Channel 2
X10
test probe
to
TP13.
(4)
Connect Channel 1
X10
test probe to TP20.
(5)
Set Channel 1 sensitivity to 0.2v per division.
(6)
Set Channel 2 sensitivity to 0.2v per division.
(7)
Position the ground-referenced sweep trace of both channels to the center
graticule
line.
6.8.3.2 Test Procedure
(1)
Observe the signal at
TP13
on Channel 2 while manually moving the positioner
carriage through
its
full stroke.
NOTE
Channel 2
output
should be a
digital
Signal
of
approximately
Ov
to
5v.
If
the digital signal cannot be
observed, repeat the
X +
90
Balance procedure detailed in
Paragraph 6.8.2.
6-19
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