Controlling Grid Bias Voltage - Canon NP6317 Service Manual

D.

Controlling Grid Bias Voltage

a. During scanning, the DC controller PCB output GRDON is '0' and CUR-LEV is '0'.
Q9 goes ON and the comparator output is '0'.
Q8 goes OFF.
Current does not flow into transformer T4, and Q10 goes ON.
Bias is applied to the grid.
The surface of the drum is charged.
The voltage applied to the grid is fixed by the shield current.
b. When scanning is not taking place, the DC controller PCB output GRDON is '1', and CUR-
LEV is '1'.
Q9 goes OFF and the comparator circuit output is '1'.
Q8 goes ON, and current flows into T4.
Bias is not applied to the grid.
Under the above conditions, the surface of the drum is not charged; hence, toner does not
adhere to it (blanking).
The timing at which the grid bias is switched may be varied using "C3" or "C6" in the service
mode (leading edge non-image width adjustment).
COPYRIGHT © 1999 CANON INC. CANON NP6317 REV.0 APR. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 4 IMAGE FORMATION SYSTEM
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