Samsung Office Master SCX-5312F, Service Manual

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Samsung Electronics
CIRCUIT DESCRIPTION
Repair Manual
3-5-4. FAN/SOLENOID ACTUATION CIRCUIT
The fan actuation circuit its power using NPN TR. When it receives ‘FAN’ signal from the CPU. The TR will turn on to make
the voltage supplied to the fan to 24V in order to actuate the fan.
The solenoid is actuated in the same way. When it receives control signal from the CPU, the solenoid for paper feeding is
actuated by switching circuit.
D29(1N4003) diode is applied to the both ends of the output terminal to protect Q22(KSC1008-Y) from noise pulse induced
while the solenoid is de-energized.
3-5-5. PTL ACTUATION CIRCUIT
PTL actuation circuit switches its power using NPN TR.
3-5-6. MOTOR ACTUATION CIRCUIT
Motor actuation circuit is determined while selecting the initial driver IC (provided by the vendor). This system uses
TEA3718(U57, U58), A2918(U59)’s motor driver IC. However, the sensing resistance (R273, R274, R292, R293) and refer-
ence resistance (R284, R289, R294, R295) can vary depending on the motor actuation current value.
It receives motor enable signal (2 phase) from CPU and generates bipolar pulse (constant-current) and sends its output to
stepping motor input.
3-5-7. HIGH VOLTAGE POWER SUPPLY
3-5-7-1. Summary
It is the high voltage power supply that has DC+24V/DC+5V (used for the image forming device in OA digital picture devel-
oping method) as the rated inputs. It supplies electrifying voltage (MHV), supply voltage (SUPPLY), developing voltage (DEV),
blade voltage(BLADE) and transferring voltage (THV).
Each high voltage supply shows the voltage required in each digital picture process.
3-5-7-2. Digital Picture Process
Digital picture developing method is widely used by copy machine, laser beam printer and fax paper.
The process is comprised of electrification, exposure, develop, transfer and fixing.
First, in the electrification process, retain constant charge at approx. -900V for the electric potential on the OPC surface by
electrifying OPC drum at approx. -1.4KV through the electrification roller.
The electrified surface of OPC is exposed responding to the video data by the LSU that received print command due to rota-
tion. The unexposed non-video section will retain the original electric potential of -900V, but the electric potential of the image
area exposed by LSU will be approx. -180V that it will form the electrostatic latent image. The surface of the photo-conduc-
tive drum where the electrostatic latent image is formed reaches the developer as the drum rotates. Then the electrostatic
latent image formed on the OPC drum is developed by the toner supplied to the developing roller by supplying roller and it is
transformed into visible image. It is the process to change the afterimage on the OPC drum surface formed by LSU into vis-
ible image by the toner particles.
While the supply roller energized with -450V by HVPS and the developer roller energized with -300V rotate in the same