Canon CP660, Service Manual

Page: 127 / 407

COPYRIGHT © 1999 CANON INC. CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
3. Black Developing Bias Generation Circuit
This circuit is controlled by three signals (Figure 4-606) from the DC controller PCB,
and generates the black developing DC bias and black developing AC bias for applica-
tion to the black developing cylinder.
The black developing AC bias drive signal is used to turn on and off the AC bias
applied to the black developing cylinder, while the black developing DC bias drive signal
is used to turn on and off the DC bias applied to the black developing cylinder.
The black developing bias level control signal, on the other hand, is used to switch the
levels of the black developing DC bias. (See Note.)
The black developing bias generation circuit contains the black toner level detection
circuit, which compares the output of the black developing AC bias and the output of the
antenna mounted inside the cartridge for output to the DC controller PCB as the black
toner level detection signal.
The DC controller PCB checks the voltage of the black toner level detection signal to
find out the level of toner when the black developing AC bias is applied to the black devel-
oping cylinder.
Figure 4-606
Note:
The black developing DC bias level for image areas is varied in response to the den-
sity command from the printer board*
1
or based on the result of image density cor-
rection control (p. 4-21).
*
1
Rear controller PCB (when making prints with the reader unit installed).
CHAPTER 4 IMAGE FORMATION SYSTEM
4-29
DC controller
PCB
Black
developing bias
generation
circuit
Black developing DC bias drive signal
Black developing AC bias drive signal
Black developing bias level control signal
Black developing
cylinder
Black toner
level
detection
circuit
Black toner level detection signal
AC
+
DC
(negative)
Black toner
level
detecting
antenna
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