Zenith H-100 Service Manual page 79

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8 < 5 PROCEDURE
Connect the oscilloscope probe to GND and CP3.
Set the probe to Xl0 and set the oscilloscope at
50 nS/division to display a 100 to 300 nS negative
goi ng pul se •
Apply power to the computer.
If the system has 8" disk drives, start the format
routine on an 8" diskette. While format is running,
adjust the PRECMP 1 control (R3) until the pulse width
displayed on the oscilloscope corresponds to the
manufacturer's suggested write precompensation for
that type of drive.
If there are 5-1/4" disk drives in addition to
8"
disk
drives in the system, start the format routine on a
5-1/4" diskette. While format is running, adjust the
PRECMP
2
control (R4) until the pulse width displayed
on the oscilloscope corresponds to the manufacturer's
suggested write precompensation for that type of drive.
I f
the system only has Heath/Zenith 5-1/4" 96 TPI
disk drives or non Heath/Zenith disk drives that require
write precompensation adjustment, start the format
routine on a 5-1/4" diskette. While format is running,
adjust the PRECMP 1 control (R3) until the pulse width
displayed on the oscilloscope corresponds to the
manufacturer's suggested write precompensation value
for that drive.
Power down the computer.
Disconnect the oscilloscope probe.
This completes write precompensation adjustment.
NOTE: All diskettes should be reformatted before being
used.
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