Ricoh D009 Service Manual page 388

Service Call Conditions
Zero cross error
The zero cross signal is detected three times even though the heater
relay is off when turning on the main power.
The zero cross signal is not detected for 2 seconds even though the
heater relay is on after turning on the main power or closing the front
door.
547 D
The detection error occurs twice or more in the 11 zero cross signal
detections. This error is defined when the detected zero cross signal is
less than 45.
Defective fusing lamp relay
Defective fusing lamp relay circuit
Unstable power supply
Fusing thermistor open (end)
The thermistor (end) detects 0°C or less for 5 sec.
551 A
Fusing thermistor (end) disconnected
Fusing thermistor (end) connector defective
Fusing temperature warm-up error (end)
This SC is generated if the following condition occurs:
The thermistor (end) does not detect an 8°C increment in the fusing
552 A temperature for 7.5 sec. just after the fusing temperature reached 45°C.
The temperature of the end thermistor does not reach the target
temperature for 31 seconds after the fusing lamps turned on.
Thermistor warped or broken
D009/D011/D012/D013/D091/D092 3-20 SM Appendix