Bias Voltage And Laserdrivetiming; Figure 2-27. High Voltage Supply Block Diagram - Epson H5200 - TM B/W Thermal Line Service Manual

If the SSCAN si~al is not detected, the printer indica~ a laser diode
LDATA
2.1.2.6 Bias Voltages and Laser Drive Timing
Figure 2-27 is a diagram of the drum charge bias voltage, image transfer bias voltage, doctor blade
bias voltage, and the developing bias voltage control circuit. These bias voltages are generated
from the +24 VDC from the high voltage supply board (PWB-F). If the printer detects a case open
condition, the interlock switch is set to OFF, which cuts the +24 VDC, which, in turn, cuts the bias
voltages.
These bias voltages are controlled by the engine controller board (PWB-A). The CH2QN (I-IV-T)
signal is the image transfer (roller) bias voltage control. While this signal is LOW, the image
transfer roller is charged to 3.2K VDC by the high vohage supply circuit. And while this signal is
HIGH, the image transfer roller is charged to --0.8K VW- The CHl:ON (Hv-C/T.R) si$# controls
the drum charge. While this signal is LOW, the PC drum is charged to -1.2K VDC.
The DB:CNT (HV-B.VR) signal is an analog signal for developing bias voltage control. lhis signal
controls the
Inter Leek
+24 VDC
Power Suppty
Board

Figure 2-27. High Voltage Supply Block Diagram

Rev. A
also indicates a laser diode malfunction.
Scanner Motor On
01
.
Figure 2-26. Laser Diode Error Detection
Engine Controller
Board
+24 VDC
. . . . . . . . . . . . . . . . . . . . . . . . .
Operating Principbs
malfunction. [f the scanner
0.2
High Voltage Supply
Board
[sec.]
Image Transfer
Bias
-3oO to -374 VDC
-1.2 K VDC