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NOTE
The thermoswitch is some distance away from the fuser heater. The actual temperature of
the fuser heater is about 50˚ C (122˚ F) higher than the temperature read by the
thermoswitch.
Failure detection
If the CPU judges the fuser faulty, it performs the following tasks:
1. It stops the output of the FUSER DRIVE signal (FSRD) (turn “L”).
2. It sets the RELAY DRIVE signal (RLD) to stop (turn “H”).
3. It sends an error message to the formatter.
The following conditions cause the CPU to judge the fuser to be faulty.
● Set-up failure: The temperature of the main thermistor does reach 40˚ C (104˚), 0˚ C
(32˚ F) when power is turned on, within 1.7 seconds from when the heater energizes, or
the temperature of the main thermistor never becomes 5˚ C (41˚ F) lower than the target
temperature during the paper passing.
● Abnormally low temperature of the main thermistor (Break in the main thermistor): The
temperature of the main thermistor stays at approximately 70˚ C (158˚ F), equivalent to
approximately 3.17 V, or lower for 4.0 seconds or longer.
● Abnormally high temperature of the main thermistor: The temperature of the main
thermistor stays at 230˚ C (446˚ F), equivalent to approximately 0.92 V, or higher for 1.0
second or longer.
● Abnormally low temperature of the sub thermistor: The temperature of the sub thermistor
stays lower than 90˚ C (194˚ F) for 2.5 seconds or longer.
● Abnormally high temperature of the sub thermistor: The temperature of the sub
thermistor stays at 280˚ C (536˚ F), equivalent to approximately 2.8 V, or higher for 0.1
second or longer.
Fuser detection
The printer detects the presence of the fuser.
The fuser is detected by the DC controller during the WAIT period. The DC controller
determines that the fuser unit is not installed if it detects the following two conditions and
then sends an error message to the formatter.
1. The FUSER DELIVERY PAPER DETECTION signal (/AFFPSSNS) indicates the
presence of paper (“L”).
2. The temperature at the sub thermistor does not exceed 40˚ C (104˚ F) after 500 ms of
fuser temperature control.
130 Chapter 5 Theory of operation ENWW