Ricoh FAX2900L Service Manual page 54

21 May, 1999 PRINTING
Fusing Control
FCU
+ 5 V
+ 5 V
Comparator
24-1
Thermistor Max
Thermistor
Thermistor Temp
24-2
FCIP05
THR SEL
4-1 4-2
Fusing Lamp
P S U
Thermofuse Thermostat
*
H547D662.WMF
There is no thermofuse in USA and Asia models.
During normal operation, the CPU controls the fusing lamp based on input from the
thermistor using the above circuit.
When the machine is turned on, or when it comes back from the Level 2 Energy
Saver Mode, it checks whether the thermistor circuit is intact by using the THR SEL
signal on the FCU. If the thermistor is connected properly, the machine begins
normal operation. If it is not, it generates an Auto Service Call (error code 9-22,
sub-code 09).
As a backup safety measure, when the temperature of the hot roller reaches
approximately 400 °C, the thermostat and/or thermofuse open.
The machine turns on the cooling fan when the fusing temperature reaches 60°C
and shuts it off when the fusing temperature drops below 60°C.
2-27