Protection System - Canon CLC 1120 Service Manual

C. Protection System
The fuse on the DC fuse PCB is designed to melt if an overcurrent occurs in any of the loads.
Or, the overcurrent protection circuit on the DC power supply PCB will turn on to stop the output
of the DC power supply.
If the overcurrent protection circuit 1 on the DC power supply PCB detects overcurrent, it will
stop output 1 and output 2; output 1 is used to drive the logic system so that its suspension will help
prevent malfunction of the copier. If the overcurrent protection circuit 2 detects overcurrent in the
drive system, on the other hand, the copier will stop output 2 only.
DC power supply PCB
Converter
circuit 1
3.3V/5V/-8V
+8V/+8VU
12V/15V
24V-F
Conversion
circuit 2
24V/38V
Sequence control
circuit
Stops output 2.
Stops outputs 1 and 2.
Figure 9-502 Block Diagram of the Protection System
Detection by
Overcurrent protection circuit 1
Overcurrent protection circuit 2
COPYRIGHT © 1999 CANON INC.
CHAPTER 9 EXTERNALS / AUXILIARY MECHANISMS
Output 1
33V,-8V,+8V,+8VU,12V,24V-F
Over-
current
detection
circuit 1
15V
Output 2
38V
Over-
current
detection
circuit 2 24V
A
B
DC power cut
relay (RL3)
Copier operation
Stops outputs 1 and 2
from the DC power
supply PCB.
Stops output 2 from the
DC power supply PCB.
Table 9-505 Protective Functions
CANON CLC1120/1130/1150 REV.0 MAR. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
DC fuse PCB
5V
A
FU901-FU906
FU940-FU941
FU921-FU925
FU931-FU939
15V,38V
Door switch
(SW3, SW4, SW5)
Turn off the power switch, and remove
the cause; then, wait for about 3 min,
and turn on the power switch.
PCBs
B
C
C
Resetting
9-11