Ricoh A151 Field Service Manual page 224

Check the voltage at CN105-2 to 5 on the main board when the
main switch is turned on.
17 volts 24 volts
Replace the main board.
Replace the scanner motor.
Is there 5 volts at CN103-11 on the main board when the scanner H.P.
sensor is actuated.
Yes No
Replace the scanner H.P. sensor.
Replace the main board.
A151/A152 6-30 FSM