Bias Control - Epson C11C605001 - DFX 9000 B/W Dot-matrix Printer Service Manual

Service Manual

2.1.3.6 Bias Control

This section describes the bias control.
A diagram of drum charge bias, image transfer bias, detach bias and developing bias control circuit
is shown in Figure 2-31. These bias generate from the +24 VDC on high voltage supply board
detected.
These bias are controlled by engine controller board (MC PWB). The TR:ON and TR+ signals are
image transfer (rol~bias control. While TR:ON signal is to LOW, the image transfer roller is
active. And, while TR+ signal is to LOW, the image transfer roller is charged to 1.2K VDC by high
voltage supply circuit. And while this signal is to HIGH, the image transfer roller is charged to
The CS/DS:ON signal control to drum charge and DETACH SAW bias. While this signal is LOW,
the DETACH SAW is charged to -1.OK VDC, and the OPC drum is charged.
The imaging cartridge has charged screen between charge wire for OPC drum and OPC drum. The
charge screen is connected 310 VDC zener diode. The charge screen control potential of OPC drum
surface to -310 VDC.
The DB:ON signal control to developing bias. While this signal LOW, the developing roller is
charge.
The developing bias is changed by image density control volume. The developing bias is controlled
bias level (-205 V to -265 VDC) by this volume. The image density is controlled so that the
developing bias level.
Interlock
24
Low Voltage
Suppry Board
Rev. A
Engine Controller
Board
24 VDC
Figure 2-31. Bias Control Circuit
Operating Principles
High Voltage Supply
Board
Image Transfer
1.2 or-O.6 K VDC
Developing
:
Bias
-205 to -265 VDC
. . . . . . . . . . . . . . . . . . . . . . .
DETACH SAW Bias
-1 .OKVDC
.
Drum Charge
r e c h a r g e
FG
Screen
-310 VDC
2-19