Controlling The Separation/Pre-Transfer Corona Current; Outline - Canon NP6251 Service Manual

D. Controlling the Separation/Pre-Transfer Corona Current

1. Outline

Figure 4-113 shows the circuit used to control the separation corona current and the
pre-transfer corona current, and the circuit has the following functions:
Turning on and off the separation/pre-transfer corona current.
Switching the separation corona current level.
Controlling the separation corona current to a specific level.
Switching the pre-transfer corona current level.
Controlling the re-transfer corona current to a specific level.
The DC component of the separation charging assembly and the pre-transfer
charging assembly is controlled to a specific current by obtaining a sampling signal from
the secondary side of the high-voltage transformer (HVT) with the aim of eliminating the
effects of changes in the environment on corona charging. (The AC transformer is
controlled to a specific voltage.)
The separation corona current is varied to eliminate the effects of changes in the
environment by measuring the surface potential of the drum and in relation to the output
of the environment sensor.
DC controller PCB
J114 J202
HVT.POST.AC
Q156 A-7
J114 J202
ROED
A-1
J114 J202
DCON
A-10
J114 J202
A-8
HVSCT
J114 J202
A-9
HVT.POST.DC
COPYRIGHT © 1997 CANON INC.
Download service manual and resetter printer at http://printer1.blogspot.com
-4
Switching
HVTOFF
circuit
-10
Switching
circuit
-1
Overcurrent
detection
circuit
-3
Switching
circuit
-2
Figure 4-113
CANON NP6350/NP6251 REV. 0 JULY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 4 IMAGE FORMATION SYSTEM
(HVT)
AC control
circuit
(negative power supply)
Constant
Drive
current
circuit
control circuit
DC transformerT402
(positive power supply)
Drive
Switching
circuit
circuit
+ - -
Constant
Drive
current control
circuit circuit
+
- -
Photosensitive drum
AC transformerT201
DC transformerT301
DC transformerT302
4-15