Ricoh FT 4015 Service Manual page 70

IMAGE FUSING 20 December 1996
11.4.4 Overheat Protection
There is an overheat protection circuit in the main board. If the hot roller
temperature reaches 245°C during the main motor off condition, or 255°C
during the main motor on condition, the resistance of the thermistor (between
CN113-1 and CN113-2) becomes too low. If the main board detects this
condition, "E-53" lights on the operation panel and power to the fusing lamp
is cut.
Even if the thermistor overheat protection fails, the thermofuse opens when it
reaches 169°C, removing power from the fusing lamp.
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