(4)
Continue to adjust
R98
until the transition region is approximately centered about
ground.
NOTE
If
crosstalk is observed, R98
must
be adjusted to ensure
that
it
does
not
exceed the
limits
specified in Step [3].
(5)
Fully retract positioner carriage.
(6)
Slowly move the positioner carriage approximately 1/2-inch closer toward the
spindle.
(7)
Observe
on
Channel 1 at
TP3
a signal change from
:::
-2v
to
2:+
2v
(refer
to
Figure 6-4).
(8)
Moving the positioner carriage further forward toward the spindle through the
index area (heads now loaded)
will again reverse the signal from
~
+
2v
to
:::
-2v.
(9)
Check that the signal remains at
:::
-2v
as
the positioner carriage is moved
through the
full stroke and that this condition is maintained to a point just prior
to
touching the front end
of
the positioner assembly at approximately cylinder
203
(cylinder
406
for
200
tpi).
(10)
Note that at approximately the point where the positioner carriage touches the
, front end of the positioner, which is approximately cylinder
204
(cylinder
408
for
200
tpi), the signal reverses once again
:::
-2v
to
:::
+
2v.
Also observe that at
each transition
pOint only a single transition from high to low or low to high
occurs.
NOTE
If
a transition does
not
occur,
adjustment
of
the
transducer assembly
position
is required. Refer to
Paragraph
6.8.5.4
for
adjustment
procedure.
6.8.5.3 Test Procedure - Channel 2
(1) Select oscilloscope Channel
2.
(2) Fully retract positioner carriage
to
the back stop.
(3)
Slowly move the positioner carriage 1/2-inch toward the spindle.
(4)
Observe
on
Channel 2 that the digital signal at
TP7
changes from a low to a high
state.
(5)
Observe,
as
the positioner carriage is moved forward through the index area (head
now loaded), the signal changes from a high to a
low state.
(6)
Observe that the signal remains low
as
the positioner carriage is moved further
toward the spindle. Ensure that this condition is maintained to a point
just
prior to
touching the front end
of
the positioner assembly.
(7) At approximately the end of the forward stroke of the positioner, the signal
reverses again from a
low to a high state. Also note that at each transition point
only a single transition
of
the logic state, from low
to
high or from high to low,
occurs.
NOTE
When the foregoing tests are satisfied, perform the
Velocity Transducer Phasing procedure detailed in
Paragraph 6.8.6.
6-23
830D
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