"
6300
6.8 STATIC POSITIONER ADJUSTMENTS
The following static measurements and adjustments are required to check the integrity
of
the position transducer signals (amplitude and polarity), the velocity transducer feedback
signal, and the voice-coil polarity. The test and adjustment procedures given in
Paragraphs 6.8.1 through 6.8.8 should be performed in the order presented.
6.8.1
X + 0 GAIN AND BALANCE
Values are given for all versions
of
the 03000 with values
for
200
tpi models parenthetically
stated.
6.8.1.1 Test Configuration
(1)
Prepare the positioner as described in Paragraph 6.7.1.
(2)
(200
tpi Only). Install a jumper between
TP1
on the Servo PCBA and
TP4
on the
Temperature And Write Compensation PCBA.
(3)
(200
tpi Only). Remove J215 from the Servo PCBA.
(4)
Set oscilloscope Channel 1 sensitivity
to
0.2v per division.
(5) Connect oscilloscope Channel 1
X10
probe
to
TP20. Connect ground lead to
TP1
.
(6)
Set oscilloscope horizontal sweep rate
to
2
~sec
per division.
(7)
Set oscilloscope trigger control
to
Line and Auto.
(8)
Manually load the heads onto the disk.
NOTE
A ground reference sweep trace is obtained
by
centering
the trace on
a particular graticule line with the vertical
input mode switch
of
the oscilloscope set to ground
position.
6.8.1.2 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 from the disk.
(2)
Monitor
TP20
on
oscilloscope Channel 1 and observe the Position Reference
(X
+
0)
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
exceeded, perform the adjustment procedures in Paragraph 6.8.1.3 before
continuing
this
procedure.
(3)
Acceptable limits:
• 13.2v (maximum) peak-to-peak
• 1 0.8v (minimum) peak-to-peak
(4)
Monitor
TP20
and observe that the variation about the mean voltage throughout
the full stroke
of
the pOSitioner is less than ± 1.2v. If the voltage variation
envelope is greater than
± 1 .2v about the mean voltage, perform the scale-flatness
adjustment in Paragraph 6.8.1.4.
6-16
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