830D
(3)
Select Channel
2.
• Return the positioner carriage to its fully retracted position.
• Observe that the digital signal at TP14 is a high state.
• Slowly move the positioner carriage approximately 1/2-inch toward the spindle
and at the same
time
observe that the digital signal at
TP14
changes from a
high to a low state.
• Continue
to
move the positioner carriage slowly toward the spindle, all the way
to the front stop. Note that the signal always remains in the low state.
NOTE
If
the
limits
in Paragraph 6.8.4.2, Steps
[2]
and
[3]
are
exceeded, refer to the
Adjustment
Procedure in Paragraph
6.8.4.3.
(4)
Perform the Index Balance procedure detailed in Paragraph 6.B.5.
6.8.4.3 Adjustment Procedure
Repeat the tests and adjustment procedures contained in
Paragraphs 6.7.1 through
6.B.4.2.
In
the event that test
limits
given in Paragraph 6.B.4.2 are exceeded after repeating
the foregoing tests and adjustments, replacement
of
the scale
or
reticle assembly or the
Servo PCBA may be required.
6.B.5 INDEX BALANCE
The
Index area is located very close
to
where
the
heads are either loaded on or unloaded
from the ramp. This
load/unload position is
within
6.35 mm ('lA-inch) from the outside rim
of
the disk.
6.8.5.1 Test Configuration
(1)
Prepare the positioner as described in Paragraph 6.7.1.
(2)
Connect Channel 1 probe
to
TP3.
(3)
Position Channel 1 ground-referenced sweep trace to the center line
of
graticule.
(4)
Connect Channel 2 probe
to
TP7.
(5)
Set Channel 1 sensitivity to 0.5v per division.
(6)
Set Channel 2 sensitivity
to
0.2v per division.
(7)
Use automatic or normal sync, internal trigger mode, and trigger
on
positive
slope.
(B)
Set sweep rate to
20
msec per division.
6.B.5.2 Test Procedure - Channel 1
(1)
Select Channel 1 .
(2)
Within the first %-inch after the heads are loaded
onto
the disk index area,
manually move the positioner carriage back and forth.
(3)
Check that the signal at
TP3
changes from :::+2v to
:5-2v
(refer
to
Figure 6-4).
Adjust potentiometer
R98
(Index Balance)
to
obtain these values.
NOTE
Clockwise adjustment
of
R98
will
bias the signal more
positive.
6-22
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