2-40 Phaser 7500 Printer Service Manual
Theory of Operation
• Center Temperature Sensor (non-contact type) - The Thermistors are electric
resistors that react to temperature changes; they are placed close to, but not
in contact with the Heat Roll to detect the surface temperature of the Heat
Roll. This controls the ON (conducting: light on)/OFF (light off) status of the
Heater Lamp based on the detected temperature.
• Rear Temp. Sensor (contact type) - The Thermistors are electric resistors that
react to temperature changes; they are placed in contact with the Heat Roll to
detect the surface temperature of the Heat Roll. This is used to prevent the
Heat Roll from reaching abnormally high temperature.
• Thermostats (x2) - The Thermostats are placed in series with the Heater
Lamp power supply. If the Temperature Sensors (Thermistors) have failed to
prevent overheating (primary), and the contact point has reached the
specified temperature, the contact will open to prevent secondary
overheating.
• Fuser Exit Sensor - Detects that paper has passed through the Fuser section.
No paper: Sensor blocked
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