Minolta Di551 Service Manual page 152

2. Protection by the hardware circuit
The output voltages from TH1 and TH2 (fixing
temperature sensors) are compared with the
abnormality judgment reference value in the
comparator circuit. If the output voltage from
TH1 or TH2 exceeds the reference value, L2
(fixing heater lamp 1), L3 (fixing heater lamp
2), L4 (fixing heater lamp 3) and RL1 (main
relay) are turned OFF in hardware means.
CAUTION:
Periodically check the TH2 face contact-
ing the roller, and replace TH2 if any
abnormality is detected.
Since TH1 (fixing temperature sensor)
face does not contact the roller, check the
distance from the roller and the sensor
orientation if any abnormality is detected.
The RL1 function must not be deactivated
under any circumstances.
3. Protection by TS1 (thermostat/U) and TS2
(thermostat/L)
When the temperature of the fixing roller
(upper/lower) exceeds the specified value, TSs
are turned OFF, thus interrupting the power to
L2 (fixing heater lamp/1), L3 (fixing heater
lamp/2), and L4 (fixing heater lamp/3) directly.
CAUTION:
Do not use any other electrical conductor
in place of TS1 and TS2. Do not change
the distance between the roller and TS
(thermostat).
S-11
SAFETY INFORMATION