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Speed Precision Abnormality
NOTE: Refer also to Chapter 9, "Board Adjustments."
1. Check the main unit feed motor control circuit.
a. During power–on, the LED (D2) on the I/O board should emit a steady light.
b. If LD2 blinks or does not light at all, turn VR5 on the I/O board
2. Check the drum motor encoder (DME).
a. Place the rotary switch in the "0" position on the MPU board.
b. Put the positive lead of the digital multimeter on pin 11 of CN29 on the I/O
c. While rotating the drum motor axis by hand, measure the voltage, which
If voltage is not normal, replace the DME after checking the harness.
3. Determine if the drum motor is overloaded.
a. Put the positive lead of the digital multimeter on R8 (E side of Q7) on the
NOTE: On the I/O board, TP2 and TP15 are printer grounds (PG).
b. Turn the power ON.
c. Measure the voltage, which should be less than 1V.
If the drum motor is overloaded (over 1.5V), check the load on the cleaner.
Remove the cleaner unit and determine if the drum voltage is below 1V. Replace
the cleaner, if necessary.
Also, raise the arm on the developing unit and determine if the voltage is below
1V. Replace the developing unit, if necessary.
4. Check the drum motor.
a. Remove the drive belt between the drum and the drum cleaner.
b. Put the positive lead of the digital multimeter on R8 (E side of Q7) on the
c. Measure the voltage. If it is not 450 50mV during drum motor operation,
7–60
counterclockwise until LD2 emits a steady light.
board, and the negative lead on the SG.
should fluctuate between 0V and 5V.
I/O board, the negative lead on the PG.
I/O board, the negative lead on the PG.
replace the drum motor.
Troubleshooting
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