Sharp AR-651 (serv.man13) Service Manual ▷ View online
AR-651/810 PROCESS SECTION 10 - 5
J347-2 HVTVR
J347-8 HVDVR
J347-5 HVMVR
BC-RAM
IC58
IC56
IC18
IC27
Gate
array
D/A
converter
Transfer
Developer
Main
Main CPU
AR-651/810 PROCESS SECTION 10 - 6
10. 5. Surface Potential Sensor
10. 5. 1. General description
The surface potential sensor detects the surface potential of the photoconductive drum and controls it to
keep constant.
10. 5. 2. Construction
The surface potential is controlled by the following construction.
• Surface potential sensor
: Detecting the surface potential of the photoconductive drum
• Control section
: Controlling to keep the surface potential constant
• High-voltage transformer
: Supplying voltage to the main charger grid
PWA-F-LGC-340/341/342
IC58
IC27
IC56
IC18
Main charger grid
Surface potential sensor
Photo-
conductive
drum
High-voltage
transformer
Control
voltage
signal
D/A converter
Gate
array
Main CPU
BC-RAM
10. 5. 3. Control method
(1) Surface potential correction control
The adjusted output value of the main grid voltage in the BC-RAM is output to the main CPU.
Then control voltage data is output to the D/A converter from the main CPU through the gate
array.
The data is converted into the analog data by the D/A converter and then amplified.
The control voltage of the main output is output to the high-voltage transformer.
The high-voltage transformer outputs the main grid voltage proportionate to the control voltage.
The surface potential sensor detects the potential on the photoconductive drum and gives it
feedback to the main CPU.
The potential is compared to the control allowable level specified in the BC-RAM.
If the potential is out of the control allowable level, the main grid voltage to be changed is
calculated from the difference between the targeted value and detection value.
The output value of the main grid voltage is changed.
AR-651/810 PROCESS SECTION 10 - 7
(2) Conrol during warming-up
When the warming-up begins, the control is carried out following (1) at the previous page and the
warming-up ends within the control allowable level.
(3) Control when finishing printing job
When the printing job has finished, the control is carried out following (1) at the previous page and the
printing operation ends within the control allowable level.
AR-651/810 PROCESS SECTION 10 - 8
Terminal cover
Latch
10. 6. Disassembly and Replacement
[A] Main charger
(1) Open the front cover and take off the front
side right inner cover, toner cartridge drive
unit and toner recycle unit. (
Chap.12.6)
(2) Remove 1 screw and pull out the main
charger.
Main charger
Main charger grid
Terminal cover
(3) Push the button to release the tension of the
main charger grid and take off the grid.
(5) Release 2 latches and take off the rear side
terminal cover.
(4) Release 1 latch and take off the front side
terminal cover.
Latch
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