Samsung SCX-4100 Service Manual page 34

4.4.1 HVPS(High Voltage Power Supply)
1) Transfer High Voltage (THV+)
- Function : It is this voltage that transfers toner from the OPC Drum to the paper.
- Output voltage : Maximum +5000V ±5% (no load, variable duty cycle)
- Error : IF THV (+) is not present, low density printing occurs due to toner on the OPC Drum not being
transferred to the paper. It is possible that waste toner over-flow can occur if this condition persists.
Ghost images may appear which repeat at 76mm intervals.
2) Charge Voltage (MHV)
- Function : It is this voltage that charges the surface of the OPC to -900V ~ -1000V.
- Output voltage : -1300V ~ -1800V DC ± 50V
- Error : IF MHV is not present toner then since the OPC drum surface has no charge toner is attracted to the
whole OPC surface. A black page is printed out when this happens.
3)Cleaning Voltage (THV-)
- Function : It removes toner contamination from the rear side of the paper by sending (-) polarity to the transfer
roller forcing toner to transfer back to the to OPC drum.
- Output Voltage : -1000VDC, +300V/-150V
- Error : Smudges and toner contamination on the reverse side of the printed page.
4) Developing Voltage (DEV)
- Function: It is this voltage that develops toner with on to the section of the OPC drum surface exposed by the
LSU (Laser Scanning Unit).
* When printing the exposed voltage on the OPC is -180V, unexposed is -970V, and the exposing voltage on
the DEV is -330V. Therefore toner with (-) polarity is developed onto an exposed section of the OPC.
- Output voltage: -200V ~ 600V DC ± 20V
- Error: a) If DEV is GND, print density gets extremely low.
b) When DEV is floating due to poor connection between the frame and cartridge contacts etc., print
density gets extremely high.
5) Supply Voltage (SUP)
- Function: It is this voltage that supplies toner to the developing roller.
- Output voltage: : -350V ~ -750V DC ± 50V (Use ZENER)
- Error: a) When SUP is GND print density gets extremely low.
b) If SUP is floating due to poor connection between the frame and cartridge contacts etc.
density gets extremely low such that it is hard to see toner with the eyes
6) OPC Ground ZENER Voltage
- Function: It is this voltage that prevents image contamination under low temperature and low humidity
environment conditions.
- When a set prints without an output voltage, -130V DC ± 15V is maintained on OPC ground. (-130V ZENER
diode is connected to OPC ground)
- Error type: a) When the ZENER diode is - 0V there is no serious image problem in general environment, but
in low temperature and low humidity environments it is possible that contamination can occur on
the entire image
b) When the ZENER diode is disconnected a blank page is printed out. (It is the same when a
ZENER diode is disconnected from OPC ground.)
Samsung Electronics
Summary of product
Service Manual
4-13