Sharp AR-651 (serv.man13) Service Manual ▷ View online
AR-651/810 PROCESS SECTION 10 - 4
10. 4. High-voltage Transformer Output Control Circuit
10. 4. 1. General description
The high-voltage transformer output control circuit is a circuit that generates the output control voltage
(Vc) for the main charger (Main), transfer belt power supply roller (Transfer), drum cleaning brush (Brush)
and developer bias (Developer).
It changes the output current linearity by changing the Vc.
10. 4. 2. Operation
PWA-F-LGC-340/341/342
PS-HVT-340
IC27
IC58
IC56
IC18
BC-RAM
Vc
Adjustment
mode
Main CPU
Gate
array
Digital
data
Analog
data
D/A
conerter
•
Each adjustment value of the Main, Transfer and Developer in the BC-RAM is output to the main
CPU.
•
The Vc data is output to the D/A converter from the main CPU.
•
The data is converted into the analog data at the D/A converter.
•
The Vc is output to the Main, Transfer, and Developer transformer.
•
The Main, Transfer, and Developer transformer generate an output current or voltage which is
proportional to the Vc.
* The adjustment of the Vc (changing of the adjusted data) is carried out at the adjustment mode.
* The output value of the drum cleaning brush bias is fixed when the high-voltage transformer is
delivered to the market.
Main
Transfer
Developer
Output
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.
