Service manual
DRUM UNIT
2-E-3
2 UNIT EXPLANATION
[5] Drum Potential Control
The drum potential is detected by the DPS (drum
potential sensor) and send the PRCB (printer control
board) via the DPSB (drum potential sensor board).
1. Operation
Drum potential control is performed to keep the
drum surface potential constant and maintain
image quality regardless of the usage environ-
ment or the number of copies.
(1) Method
The image is created on the drum surface by the
difference in the exposure potential and develop-
ing bias. A patch is created with laser PWM max-
imum.
The developing bias is corrected so that the dif-
ference between the after exposure potential
(solid black area) and the developing bias is
always kept constant and the charging current
and the grid voltage are corrected so that the dif-
ference between the before exposure potential
and developing bias is always kept constant.
(2) Timing
a) When the fixing temperature is lower than
50°C at power ON.
b) At the end of job after every 5,000 copies.
2. Signals
a. PRCB Input signals
(1) DPS ANG (DPSB to PRCB)
Analog signal corresponding to the drum charg-
ing potential.
b. DPSB Input signals
(1) DPS ANG 1 and 2 (DPS to DPSB)
Analog signal corresponding to the drum charg-
ing potential.
c. DPSB output signals
(1) DPS DRIVE A and B (DPSB to DPS)
DPS (drum potential) drive signal.
DCPS2
PRCB
DPSB
DPS
24VDC
PGND
DPS DRIVE A
DPS DRIVE B
DPS ANG 1
DPS ANG 2
DPS ANG
SGND
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