Ricoh A151 Field Service Manual page 242

No
Check that CN113 on the DF main board and CN121 on the pulse
generator sensor are correctly connected.
Correct Incorrect
Connect CN113 and CN121.
Turn on DIP switches 1, 3 and 4 on the DF main board and turn on the lift
switch. Check the voltage at CN113 on the DF main board.
1.5 volts 0 volts
Replace the pulse generator sensor.
Replace the DF main board.
A151/A152 6-48 FSM