Oce 3121 Technical & Service Manual page 565

Protection circuits
The following circuits are incorporated to prevent malfunctioning of the heat-
er:
Thermistor TH1, TH2
1
The DC control PBA monitors the signals from the thermistors TH1 and
I
TH2. If an exceptionally high or low temperature is detected, the machine is
switched OFF. Codes E000 through to E003 will be logged.
The maximum acceptable reading from for TH1 is 250°and for TH2 it is
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260°C. The heater error detection signal (HTNG) is issued, isolating the ma-
chine.
Thermal fuse (FU1)
2
If the ambient temperature at the thermal fuse reaches 226 °C, and remains at
that level for a certain period, the thermal fuse will melt, interrupting the power
to the heater.
Heater ON detection circuit (200V model only)
3
The time during which the heater drive signal (HTRD) remains OFF is moni-
tored. If an error is detected, the power is switched OFF. (E004 is logged)
508 TSM Océ 3121 Functional description