Canon CP660 Service Manual page 219

See Figure 6-202 and the following text for the functions of the circuit:
The fixing heater safety circuit in the power supply monitors the upper fixing roller
temperature detection signal (FXTHU) at pin No. 14. When increases in the fixing tem-
perature causes the output voltage of the upper thermistor to be about 1.4 V, the output
of pin No. 13 of IC101 goes '1', and the signal at pin No. 14 of the fixing heater safety cir-
cuit will be '1'. In response, the fixing heater safety circuit causes the output of pin No. 5
to go '0'.
Then, Q111 of the fixing assembly error detection circuit turns off to turn off Q112 and
thereby to turn off the relay (RL101), cutting off the power to the upper fixing heater and
the lower fixing heater.
b. If the fixing heater safety circuit finds a fault in the lower fixing heater,
The fixing heater safety circuit is in the power supply and, if an abnormal increase
occurs in the fixing temperature, it cuts off the power to the upper and lower fixing
heaters.
See Figure 6-202 and the following text for the functions of the circuit:
The fixing heater safety circuit in the power supply monitors the lower fixing roller tem-
perature detection signal (FXTHL) at pin No. 14. When increases in the fixing tempera-
ture causes the output voltage of the upper thermistor to be about 1.4 V, the output of pin
No. 9 of IC101 goes '1', and the signal at pin No. 14 of the fixing heater safety circuit will
be '1'. In response, the fixing heater safety circuit causes the output of pin No. 5 to go '0'.
Then, Q111 of the fixing assembly error detection circuit turns off to turn off Q112 and
thereby to turn off the relay (RL101), cutting off the power to the upper fixing heater and
the lower fixing heater.
3. Fixing Assembly Error Detection Circuit (in the power supply circuit)
This circuit is in the power supply, and monitors the fixing assembly for an open con-
dition of the thermal switch and the fixing heater for an open circuit.
a. Displaced Fixing Assembly (E009)
The fixing assembly error detection circuit checks to find out whether the rated volt-
age of the power supply and the rated voltage of the fixing assembly match. For instance,
if a 100-V power supply and a 220V fixing assembly are connected, it will identify a rated
voltage mismatch. If the fixing assembly is not mounted, the expansion I/O (IC203) on the
DC controller PCB will assume a fixing assembly type mismatch, and communicates the
fact to the printer board*
The rated voltage of the power supply is set by means of a jumper wire (JP1; for a
100V power supply, JP1 is open, while JP1 is shorted for a 200V power supply). The set-
ting is monitored by the expansion I/O using the power supply type detection signal
(ACTYP).
The rated voltage of the fixing assembly, on the other hand, is set by means of a
jumper wire (JP2) inside the fixing assembly (for a 100-V fixing assembly, JP2 is open,
while it is shorted for a 200-V model). The setting is monitored by the expansion I/O as
the fixing assembly type detection signal (FXTYP).
If the rated voltage of the power supply and the rated voltage of the fixing assembly
do not match, the expansion I/O will identify the condition as displacement of the fixing
assembly.
COPYRIGHT © 1999 CANON INC.
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CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 6 FIXING SYSTEM
6-7