Read Sharp AR-810 (serv.man14) Service Manual online
AR-651/810 PROCESS SECTION 10 - 1
10. PROCESS SECTION
10. 1. Construction
This chapter describes the image formation process related units, parts and control circuit, etc. Mainly
included in this chapter are the followings.
• Main charger
• Charger wire cleaner
• Discharge lamp
• Ozone filter
• High-voltage transformer
• Surface potential sensor
• Exhaust duct
The drum/cleaner unit, developer unit and transfer belt unit are described in other chapters.
Charger wire cleaner
Surface potential sensor
AR-651/810 PROCESS SECTION 10 - 2
10. 2. Functions
The drum is a cylindrical aluminum base which has thinly applied to it an organic photosensitive mate-
rial. The photosensitive material produces an electrical current when exposed to light. The amount of
current produced is indirect proportion to the light intensity and exposure time.
(2) Main charger
The main charger is configured by stretching a thin wire between two insulation blocks provided at both
ends of the U-shaped metal housing.
When a high voltage is applied to the charger wire, the air around the wire is ionized (electro-statically
charged), and this ionized air is attracted onto the drum’s surface. This phenomenon is referred to as a
“corona discharge”. In the dark, the surface of the drum is negatively (–) charged by the corona dis-
charge of the main charger.
(3) Charger wire cleaner
The charger wire cleaner removes contamination collected on the charger wire. It moves backward and
forward to clean the charger wire after the power is turned ON and more than 2000 continuous copies
have been made since the door switch was turned ON or the previous cleaning operation was per-
(4) Discharge lamp
Discharging is the process of reducing or eliminating unwanted electrostatic charges on the drum.
The discharge lamp has two effects, a cleaning effect and pre-exposure effect. By the cleaning effect, it
neutralizes and eliminates the residual charges on the drum surface by exposing it to light. The pre-
exposure effect ensures a fixed drum surface potential before the next charging process.
(5) Ozone filter
The ozone filter decomposes ozone by exposing it to activated charcoll the ozone has been generated
through the corona discharge of the main charger, and is forced through the filter by the exhaust fan.
(6) Surface potential sensor
The surface potential sensor detects the surface potential of the OPC drum and controls it to keep the
copy quality constant.
AR-651/810 PROCESS SECTION 10 - 3
10. 3. Charger Wire Cleaner Operational Circuit
(1) Role of the charger wire cleaner circuit
This circuit is for cleaning the main charger wire. It reciprocates the wire cleaner regularly to avoid
a poor charging and irregularities of the drum.
(2) Configuration of the charger wire cleaning circuit
• Wire cleaner drive motor
: Driving of the wire cleaner
• Wire cleaner stop position switch : Detection of the wire cleaner reaching the limit (rear side)
• Control section
: Controlling of the cleaner drive unit and cleaning of the wire
Drive unit control signal
Reverse rotation (Home position
Forward rotation (Limit
MCLSW-0 (Stop position switch)
Main charger wire
Stop position switch input signal
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
Each adjustment value of the Main, Transfer and Developer in the BC-RAM is output to the main
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.