Xerox Phaser 6120 Service Manual page 270

Heater Lamp (H1) is turned OFF forcibly and the initiation of any new print cycle is
prohibited (abnormally high temperature detection control).
Hard Protection (Hard Stop)
Circuitry within the PWB-A Controls a relay that shuts down the power supply to the
Heater Lamp (H1) when an abnormal temperature is detected.
Thermostat Protection
If neither the soft protection nor hard protection can detect an abnormally high
temperature due to a defective Thermistor (TH1) or other reason, the Thermostat (TS1)
operates at the specified temperature. This shuts down the power supply to the Heater
Lamp (H1), thus forcibly turning it OFF.
Heater Lamp
Thermistor
Thermostat
Fusing PressureRoller
Laser Safety Switch
Triac Circuit
Power Switch
PPM (Pages Per Minute) Control
PPM control is provided to prevent the temperature on edges of the Heating Roller from
increasing during a multi-print cycle using plain paper of a small size.
The distance between sheets of paper is widened according to the number of printed pages
set to be produced and the paper length. This evens out the temperature of the Heating
Roller and thus stabilizes fusing performance of the printed toner image.
To perform the PPM control, the number of printed pages per minute is established for
each paper size.
Phaser® 6120 Color Laser Printer Service Manual
5V
Mechanical Control Board
A/D
Heating Roller
GND
Hard Protection
Circuit
FUSER WDT
Watchdog Circuit RESET
Heater Remote
ON/OFF
7-50
Print Engine Theory of Operation
CPU
4139to2097e0