There are two overvoltage devices in this product:
● Fuse F101 provides overcurrent protection for the fusing system circuitry.
● Fuse F102 (110V products only) provides overcurrent protection to the printer DC power
supply circuitry.
You can check or replace the fuses by removing the left cover. If either of these fuses fail,
replace the engine power assembly.
High-voltage power distribution
The high-voltage power supply applies an overlap of DC and AC voltage to the primary
charging roller and to the developing roller. This circuit also applies a positive or negative DC
voltage to the transfer roller according to the instructions from the engine control unit.
This circuit also controls the image density by changing the primary AC voltage and the
developing AC bias according to the print density setting (which is set using HP Toolbox).
High voltage is disabled when the print cartridge door is open.
PR1
TRS
DEV
IC902
CPU
DVAC
TRNDC
TRCRNT
TRPDC
PRAC
PRPWM
IC301
IC301IC301
IC301
IC501
Positive voltage
generation circuit
J303
J304
J301
J302
DC voltage
generation
circuit
AC voltage
generation
circuit
DC voltage
generation
circuit
AC voltage
generation
circuit
Combined
Combined
Primary
charging roller
Developing
cylinder
Transfer
charging
roller
Engine controller PCB
High-voltage power supply circuit
Developing bias circuit
Transfer charging bias circuit
Negative voltage
generation circuit
Photosensitive
drum
Primary charging bias circuit
J201-14J902-10
J201-15J902-9
J201-16J902-8
J201-18J902-6
J201-17J902-7
J201-22J902-2
Power supply PCB
Figure 4-4. High-voltage power supply circuit
42 Chapter 4 Operational overview ENWW
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