KPOWERSCIENCE KP3828 Series, Maintenance Manual

Page: 206 / 230

8-34
[2C Toner density too low]
Procedure Points to be checked Remedy Checking method
1 Is the KMPU board
normal? If YES, go to 2.
If NO, replace the
KMPU board
(malfunction of the
toner density
sensor interface
circuit).
Disconnect CN6 of the KMPU board
and bring the positive lead of a digital
multimeter in contact with the collector
of Q11 (2SC2120) of the KMPU board
and the negative lead in contact with
SG, and measure the voltage.
If normal, the voltage will be
approximately 5 V when the power is
turned on and will be approximately 0
V when pin 15 of CN6 of the KMPU
board and pin 29 (5V) of CN6 are
shorted.
2 Is the developing unit
normal? If YES, go to 3.
If NO, replace the
developing unit
(toner density
sensor abnormal.)
Connect CN6 of the KMPU board.
Disconnect pin 14 of CN6 of the
KMPU board. Bring the positive lead
of a digital multimeter in contact with
the collector of Q11 (2SC2120) of the
KMPU board and the negative lead in
contact with SG, and measure the
voltage.
If normal, the voltage will be
approximately 0 V when pin 14 of CN6
of the KMPU board and pin 29 (5V) of
CN6 are shorted.
3 Is the toner supply
clutch normal? If YES, go to 4.
If NO, go to 4.
Connect pin 14 of CN6 of the KMPU
board. If normal, the toner supply
sponge roller will rotate when the
“Request for Engine Operation”
command for “execution of toner
supplying” is issued.
4 Is the control voltage of
the toner density sensor
normal? If NO, replace the
KMPU board
(toner density
sensor control
voltage error). Bring the positive lead of a digital
multimeter in contact with pin 14 of
CN6 of the KMPU board and the
negative lead in contact with SG (J7),
and measure the voltage. If normal, the
voltage will be approximately 0V~12V.