2-16 Phaser 6121MFP Service Manual
Theory of Operation
Print Control Temperatures
• The Fuser Roller temperature is set according to the type of media, main body
interior temperature (as measured by the temperature/humidity sensor), and
warm-up start decision.
• For types of media other than plain paper, the fusing speed is controlled at the
1/2 speed.
Print Control Temperature Adjustments
• The temperature during print control is adjusted using the menu available
from the control panel.
• Adjustment steps are 0°C, -5°C, and -10°C.
Protection Against Abnormally High Temperature
The machine provides protection at three different stages to prevent abnormally
high temperature of the Fuser.
Soft Protection
If the Thermistor (TH1) detects a temperature exceeding a predetermined value,
the malfunction code representing abnormally high temperature is displayed. At
this time, the power supply line is shut down.
If the temperature of the Fusing Roller does not reach a predetermined value
within a predetermined period of time after the start of the warm-up cycle, the
power supply line is shut down.
Hard Protection
If the CPU overruns and the output level of the CPU of the Mechanical Control
Board becomes a HIGH or LOW level, and not a pulse output, and a predetermined
temperature or higher is detected, a circuit within the Mechanical Control Board
turns OFF the relay to shut down each power supply line.
Thermostat Protection
If a faulty Thermistor (TH) prevents detection of abnormally high temperatures by
soft protect or hard protect, the thermostat operates at a predetermined
temperature to shut down the power supply line.
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