Xerox Phaser 3450 Service Manual page 23

4.3.1. HVPS(High Voltage Power Supply)
1) Transfer high voltage (THV (+))
- Function : It is a voltage that transfers toner on an OPC Drum to paper.
- Output voltage : MAX +4.2 KV +/- 5% (Duty is changeable, Not loading)
- 1.6KV +/- 15% (When cleaning, 200MOhm - It transfers toners with (+) polarity of transfer roller to an OPC Drum.
- Error type : IF THV (+) is not outputted, it causes a low density due to toner on an OPC Drum if it is not transferred to
paper. It is possible that over-flow occurs if toner is piled up in a toner vessel continuously.
2) Charge voltage (MHV)
- Function : It is a voltage that charges a surface of OPC to -750V~-900V.
- Output voltage : -1.3KV~1.5KV DC +/- 50V
- Error type : IF MHV is not outputted, toner overflows and reaches to an OPC drum if surface of an OPC is not
charged. A black paper is printed out when it happens.
3) Cleaning voltage : THV (-)
- Function : It removes contamination at a rear by sending (-) polarity in a transfer roller to OPC drum to take toner.
- Output voltage : A change range is large according to a load because there is no feedback control =(-600V~-1200V)
- Error type : An error due to contamination of toner on a backside of printing paper.
4) Developing voltage (DEV)
- Function : It is a voltage that develops toner with electronic potential difference of the section exposed by LSU (Laser
Scanning Unit).
* When printing, exposing voltage of OPC is -250V and exposing voltage of DEV is -470V. Therefore,
toner with (-) polarity is developed on an exposed section.
- Output voltage : -400V~470DC +/- 20V
- Error type : a) If DEV is GND, a density gets extremely low.
b) When DEV is floating due to instable of terminal's contacting point, and etc., density gets extremely
high.
5) Supplying voltage (SUP)
- Function : It is a voltage that supplies toner to a developing roller.
- Output voltage : -580V~650V DC +/- 50V (Use AENER, Gearing of DEV - (-)180V more than DEV)
- Error type : a) When SUP is GND, density gets extremely low.
b) If SUP is floating due to instable of terminal's contacting point, and etc., density gets extremely low
that it is hard to catch up with eyes.
6) OPC Ground ZENER voltage
- Function : It is a voltage to prevent an image contamination under the condition of low temperature and low humidity
environment.
- When a set prints without an output voltage, -100V is maintained on OPC ground.
(-100V AENER diode is connected to OPC ground)
- Error type : a) When ZENER diode is - 0V, there is no serious image problem in general environment, but in low tem-
perature and low humidity environment, it is possible that a contamination occur on entire image
b) When ZENER diode is disconnected, a blank page is printed out. (It is the same case as when a
ZENER diode is disconnected to OPC ground.)
Summary of product
Service Manual
4-11