Overheat Protection - Ricoh Aficio 1515 Service Manual

9 March 2004

Overheat Protection

The BICU references the fusing temperature through the thermistor [A]. The copier
prevents overheating as listed below. Normally, Feature 1 is effective in preventing
overheating. Features 2 through 3 are fail-safe features.
Feature 1:
The BICU turns off the fusing lamp when the fusing temperature is too high.
Feature 2:
The BICU disables the machine operation when the thermistor detects an
abnormal temperature transition. In a case like this, the copier displays one of the
following SC codes (☛ 4.1.2): SC543, SC544, SC545, SC546.
NOTE: If the fusing temperature is too low, SC542 is displayed.
Feature 3:
The BICU disables the machine operation when the thermistor does not normally
work. In a case like this, the copier displays SC541 (☛ 4.1.2).
Feature 4:
The thermoswitch near the center [B] cuts the power supply to the fusing lamp at
160°C; the thermoswitch near the end [C] cuts the power supply to the fusing lamp
at 170°C. These thermoswitches and the fusing lamp are on the same circuit.
NOTE: 1) Thermoswitch temperature is somewhat lower than the fusing
temperature.
2) The thermoswitch near the center does not necessarily work earlier than
the other thermoswitch. The ends of the hot roller can be much hotter
than the center when, for example, the paper of a small size is
continuously going through the fusing unit.
Feature 5:
The BICU disables the machine operation when the exhaust fan does not normally
work. In a case like this, the copier displays SC590 (☛ 4.1.2). Note that defective
exhaust fans may cause overheating.
IMAGE FUSING AND PAPER EXIT
6-11