Zenith H-100 Service Manual page 75

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KIT BUILDER METHOD
Remove the controller board from the computer.
Remove U9, U22, and U30 from their sockets.
Tack solder a length of wire between pins 1 and 20 of
the socket for U9.
Tack solder wires to interconnect pins 30, 33, 37, and
20 of the socket for U22.
Set the PRECMP 2 control (R4) to a fully clockwise
position.
Set the PRECMP 1 control (R3) to a fully counterclockwise
position.
Connect the common test lead of the multimeter to the
GND test point.
Reinstall the controller board into the computer.
Connect the positive test lead to the CP2 test point
and apply power to the computer.
Adjust the BIAS control (R2) until the multimeter display
shows +1.40 VDC (+.05 volts). You will want to switch
the multimeter to lower ranges to perform this adjustment
accurately.
Allow a period of 15 minutes for drifting; then perform
the R2 adjustment again.
Power down the computer and remove the controller board.
Tack solder a length of wire between the two holes marked
CAL.
Reinstall the controller board and apply power to the
computer.
Adjust the FREQ control (R1) for a multimeter display
of +1.40 VDC (+0.05 volts) at test point CP2.
Power down the computer and remove the controller board.
Remove all the temporarily installed jumper wires.
Install U9, U22, and U30 in their respective sockets.
Reinstall the controller board into the computer.
The adjustments to the Data Separator are now complete.
Proceed to WRITE PRECOMPENSATION ADJUSTMENTS.
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