
3: Operation
3-104
Colorwriter LSR 2000 Printer
Service Guide
If the fixing heater safety circuit detects a
malfunction in the fixing heater
The fixing heater safety circuit in the power supply unit will shut
OFF the power supplied to the fixing heater if the fixing
temperature rises abnormally.
The operation of this circuit is shown in Figure 3-81 on page 3-105.
The safety circuit IC (Z4) in the power supply unit monitors the
fixing temperature detect signal (THI) sent to pin No. 14. If the
voltage output from the thermistor becomes about 1.6V with an
increase in the fixing temperature, the safety circuit IC will set the
output of pin No. 5 to “L” and turn off the relay (RL) to shut off
the power supplied to the fixing heater.
Simultaneously, the safety circuit sensing signal (SFSNS) sent to the
CPU on the DC controller becomes “H.” With this setting, the
CPU assesses that a failure has occurred in the fixing unit and
notifies the video controller of a power supply failure.
To reset this circuit, first turn off the printer for about 30 minutes,
and then turn it on again.