(3)
Manually move the positioner carriage
bacK
and forth through
its
full stroke,
while monitoring the waveform at
TP13
and TP20.
At
the same
time
(using a
wide-edge screwdriver in the grooves provided at the top
of
the receiver post)
rotate the reticle CW
or
CCW until the waveform
of
Figure
6-S
is achieved.
NOTE
If
more than one peak is seen on the oscilloscope screen,
choose the peak with the greatest amplitude correspond-
ing
to the correct location
of
the'
Step. '
(4) Partially tighten the hex-head screw, loosened in Step (1),
to
the
point
where self-
rotation
of
the receiver post is inhibited.
NOTE
This prepares the receiver
post
for
the Dynamic
Reticle-to-Scale
Adjustment
contained in Paragraph
6.9.3.
(S)
Perform the Heads Retracted Signal Check described in Paragraph 6.8.4.
6.8.4 HEADS RETRACTED
SIGNAL CHECK
The Heads Retracted Signal Check is made
to
acertain the approximate position at which
the signal occurs and
to
determine
if
the voltages generated are
within
acceptable
limits
and have the correct polarity.
6.8.4.1 Test Configuration
(1) Prepare the positioner
as
described in Paragraph 6.7.1.
(2) Connect Channel 1 test probe
to
TP6.
(3)
Connect Channel 2 test probe
to
TP14.
(4) Set Channel 1 sensitivity
to
O.Sv
per division.
(5) Set Channel 2 sensitivity
to
0.2v per division.
(6)
Use automatic
or
normal sync, internal trigger mode, and trigger on positive
slope.
(7)
Set sweep rate
to
20
msec per division.
(8)
Manually load the heads onto the disk.
6.8.4.2 Test Procedure
(1) Move the positioner carriage
to
its
fully
. retracted position. Note that the spindle
speed decreases as the heads are unloaded.
(2) Select Channel 1 .
• Check that the ac level
of
the signal at TP6
is:::-2v
(refer
to
Figure 6-4).
• Slowly move the positioner carriage approximately 1i2-inch toward the spindle
and at the same
time
observe that the signal at
TP6
changes in dc level from
:::
-2v
to
~
+
2v.
• Continue
to
move the positioner carriage
slowly
toward the spindle all the way
to the front stop. Check
that the signal voltage remains at
~
+
2v
as
shown in
Figure 6-4.
NOTE
There
may be some crosstalk present on the signal;
however, the voltage tolerances specified above
must
be
met.
6-21
830D
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