Zenith H-100 - Page 76

5-160
WRITE PRECOMPENSATION ADJUSTMENTS
Located on the following pages are two methods to adjust
write precompensation. The first method uses the
calibration circuit board that is included in the H-207
ki t. The second method requires the use of an oscilloscope
and precompensation data about the drives that are used
with the controller board. The first method is the
preferred method because of its ease. The second method
is required. however, when precompensation values not
included on the calibration circuit board are needed for
a particular drive. Locate the procedure you wish to use
and follow the steps in that procedure.
CALIBRATION CIRCUIT BOARD METHOD
The calibration circuit board method is primarily used to
adjust the H-207 for use wi thin a H/Z-100. By using this
method, the 5-1/4" drive section of the controller board
is set for a write precompensation value of 120 nS. This
is the value used for Heath/Zenith 48 TPI, 5-1/4" disk
drives that are included in the H/Z-100s. The jumpers at
JO and J2 remain at the stock position. That is, JO is
out and J2 is in the 8 < 5 position (foil bridge).
Yo u may use the Gal ibration circui t board for other val ues
of precompensation. By installing DL502, you may choose
from five values of precompensation. These being 120 nS,
160 n S. 200 n S, 240 nS, and 280 nS. However, you may have
a customer application that requires a precompensation value
not mentioned above. In this case, proceed to Oscilloscope
Method of Wri te Precompensation.
You may also use the calibration circuit board for setting
write precompensation for 8" disk drives. Again, if the
precompensation value needed is not obtainable with the
cal ibration board, use the Oscilloscope Method. Remember
when setting precompensation for 8" drives, you will have
to determine if the 8" value is greater than the 5-1/4"
value. If it is. you will have to jumper J2 so it is in
the 8 > 5 position. Also remember, that R4 is the control
that needs to be adjusted instead of R3.