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5.12
CONE CENTERING CHECK
Cone centering is the ability of the cone clamping mechanism to center
the
diskette
on
the hub, causing it to rotate concentrically.
This
check
and adjustment should be made whenever the upper plate assembly
has
been
removed
or
replaced.
It
the
cone
centering cannot be
aOJusted, verify the measurement with a second diskette.
1.
Set up the oscilloscope:
Channel A:
Channel B:
Test Point 4
Test Point 5
Vertical Amplitude:
100 millivolts per division
Ciround:
Test Point 8 or 14
Read Differentially:
A and H, B inverted
Time Base:
20 microseconds per division
External Trigger:
Test Point 12, positive edge
2.
Apply power to the drive.
3.
Select the drive.
4.
Seek to Track O.
5.
Write a 2F pattern on Head O.
6.
Measure the amplitude of the signal by positioning the
deepest dip in the signal on the center vertical graticule.
7.
Release the front latch, and remove the diskette.
8.
Reinsert the diskette, and close the front latch.
9.
Repeat Steps 7 and 8 until the deepest dip in the waveform
is produced.
10.
Measure the amplitude of the deepest dip.
11.
Divide this measurement by the measurement in Step 6, and
multiply it by 100.
This result should be above 85 percent.
12.
The signal amplitude should not decrease below 85 percent of
the average amplitude at any point on the track.
5-19
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