Xerox 4400DT - Phaser B/W Laser Printer, Service Manual, Page: 439 / 503

8-26 Phaser 4400 Laser Printer Service Manual
Laser Trouble (U2 Error Code)
There are three major causes of U2 errors:
1. Warm-up failure - SOS signal intervals are longer than the READY reference
value during three consecutive samplings of the SOS. The actual laser power does
not equal the value set in NVRAM.
2. Laser speed too low (Down Failure) - SOS signal intervals are longer than the set
Down Failure interval after completion of warm-up. The set Down Failure is a
time interval corresponding to 90% of the rated Laser Motor speed of rotation.
3. Laser speed too high (Overrun Failure) - SOS signal intervals are shorter than the
set Overrun Failure interval after completion of warm-up. The set Overrun Failure
is a time interval corresponding to 102% of the rated Laser Motor speed of
rotation.
Fuser Control
Fuser Temperature Control
To maintain the temperature of the Fuser Heat Roller at the levels required for proper
operation, the Fuser uses a Thermistor to monitor the temperature on the surface of
the Heat Roller. The Engine Logic Board compares that temperature with the rated
temperature that is set in NVRAM, and switches the Heat Rod on or off depending on
how the actual temperature differs from the rated temperature.
Fuser Temperature Adjustment
You can adjust the rated Fuser temperature by changing the Fuser Configuration from
the Tray Setup Menu.
The printer switches on the Heat Rod when the Fuser temperature falls below the
current control temperature (approximately 178
°
C for the standard control
temperature). The printer switches off the Heat Rod when the Fuser temperature rises
above the current control temperature (approximately 180
°
C for the standard control
temperature).
Fuser Warm-up
Power to the Heat Rod is applied at the start of printer warm-up. Warm-up is
complete when the Heat Roller reaches the current control temperature. If the Fuser
temperature is below 100
°
C at start of warm-up, then warm-up finishes when the
Fuser temperature reaches “standby temperature”.