Power Supply Pcb; Protection Mechanism For Power Supply Circuit - Canon PC400 Service Manual

CHAPTER 7 EXTERNALS/AUXILIARY MECHANISMS
B. Power Supply PCB
The copier's power supply is a composite power supply in which one main trans-
former (T106) supplies DC power as well as power for high voltage and scanning lamp.
AC power is supplied to the DC power supply when the power switch and door
switch are turned ON.
The DC power supply generates +24 V and +5 V.
For auto power-off, the microprocessor causes the relay (RL101) to go OFF, thus
cutting power supply.
The copier is equipped with a sub power supply which provides the microprocessor
with +5VDCL power for about 5 minutes after a condition associated 'E0' occurs; during
this period, the copier is prevented from going ON to prevent damage by overheating
the fixing heater.
Note:
The tolerances for the DC power supply are as follows:
• +24VR ± 5%
• +24 VU : +22 V to +46 V
• +5 VL ± 2%
• +5 V ± 10%
C. Protection Mechanism for Power Supply Circuit
The DC power supply circuit's AC power supply input is equipped with a fuse. The
fuse blows if an overcurrent flows because of a short circuit in the 24V power, thus shut-
ting out the output from the AC power supply circuit. If this happens, disconnect the
copier's power cord, correct the cause of the problem, and replace the fuse.
If the microprocessor detects an error on the AC or 24VDC line of the main trans-
former (T106), it causes the relay to go OFF, thus cutting the power output. If this hap-
pens, remove the cause and switch the copier ON to reset.
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COPYRIGHT © 1998 CANON INC. CANON PC400/420/430,FC200/220 REV.0 JAN.1998 PRINTED IN JAPAN (IMPRIME AU JAPON)