Paper Size Sensing Problem; Regularly Spaced Marks - IBM 3112 Service Manual

board. If the voltage is correct, check the continuity of the fan/mirror
motor cable. Replace the printhead if the cable is good.

Paper Size Sensing Problem

(The printed area does not fit on the page, or the paper size cannot be
changed from the operator panel.)
Make sure the paper tray and its stops are undamaged. Make sure the
cable to the paper size switch is connected correctly. With the paper
tray removed, the resistance of the paper size switch should be infinite.
With the tray installed, the resistance of the switch varies with the paper
size.
For Tray 1, remove the front cover, disconnect the cable from the sen-
sor and measure the resistance between the two pins on the sensor
board.
For 500-sheet option, remove the RIP Board, disconnect J15 from the
engine board, and measure between J15-3 and J15-4 on the cable.
If the readings do not match the following within 5% replace the paper
size sensor.
Tray installed and set to:
A5
B5
10.5"
11"
A4
13" or 14"

Regularly Spaced Marks

This is caused by a defect on one of the rolls or gears in the print pro-
cess. The damaged part can be determined by the spacing of the
marks according to the following table. Find and replace the damaged
part.
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Service Manual
1.4K Ohms (tray 1 only)
2.0K Ohms
3.0K Ohms
4.7K Ohms
8.0K Ohms
17.8K Ohms (legal tray)