4560/4570 FUSER
12 - 6
Nov. 1997 © TOSHIBA
12.4.2
Detection of thermistor burnout
* Since thermistor burnout detection circuits of the thermistor-1 and -2 are common, it is explained
with the thermistor-1.
R34
+5
R24
R23
C14
R22
HTRTH-
IC35
PC0/AN0
Main
processor
Thermistor-1
•
The input voltage is obtained by voltage divid-
ing R34, thermistor, R24 and R23.
•
The surface temperature of the heat roller
changes.
The thermistor resistance value changes
The input voltage also changes
•
The main processor detects an abnormality
thermistor broken
12.4.3
Control for abnormal heater condition
When something abnormal occurs in the heater turn-on circuit, such as a shorted TRIAC, it may become
incapable of ON/OFF control. In this case, the microcomputer detects abnormal temperatures through
the first and second thermistors, determines the corresponding error codes and counter values, and
causes the main power to be switched OFF to protect the fuser unit.
(1) Temperature detection
The following abnormal temperatures are detected by the respective thermistors:
First thermistor:
230°C
Second thermistor: 270°C
(2) Error codes
“C44”:
Displayed when keys C/S + 8 are pressed simultaneously at the time of Call
Service.
Counter value “9”: Displayed when you input “89” in the AD ( 0 + 8 ) mode.
(3) Machine condition
After de-energizing all outputs (heater lamp, exposure lamp, control-panel displays, motors, etc.),
the microcomputer causes the main power to be switched OFF.
(4) Corrective action
After the error code and counter value in (2) have been determined, abnormal temperature detection
in (1) continues. So, if the main switch is turned ON immediately, it will be turned OFF again as long
as the temperature on the heater surface remains above the abnormal detection temperatures of
thermistors. Thereafter, this will be repeated. So, after waiting for the heater surface temperature to
drop, turn ON the main switch and you can check the counter value before the main switch is turned
OFF again. After confirming that an abnormal heater condition has occurred, repair the problem and
then clear code 89 of the AD ( 0
+ 8 ) mode with “0”. After that, you can bring the copier into its normal
operating condition.
R22
IC35
Summary of Contents for 4560
Page 210: ...Nov 1997 TOSHIBA 13 43 4560 4570 ADU 13 8 7 Harness connection diagram ...
Page 213: ...4560 4570 ADU 13 46 Nov 1997 TOSHIBA 13 8 9 PC board assembly ...
Page 238: ...Nov 1997 TOSHIBA 14 25 4560 4570 CIRCUIT DIAGRAMS 14 5 Power Supply Circuit PS ACC A 115V ...
Page 239: ...4560 4570 CIRCUIT DIAGRAMS 14 26 Nov 1997 TOSHIBA B 230V ...
Page 243: ...Nov 1997 TOSHIBA 16 1 4560 4570 PC BOARD 16 PC BOARD ASSEMBLY 16 1 PWA LGC ...
Page 244: ...4560 4570 PC BOARD 16 2 Nov 1997 TOSHIBA 16 2 PWA PNL ...
Page 245: ...Nov 1997 TOSHIBA 16 3 4560 4570 PC BOARD 16 3 PWA KEY1 16 4 PWA KEY2 ...
Page 246: ...4560 4570 PC BOARD 16 4 Nov 1997 TOSHIBA 16 5 PWA ERS ...
Page 247: ...Nov 1997 TOSHIBA 16 5 4560 4570 PC BOARD 16 6 PS ACC A 115V ...
Page 248: ...4560 4570 PC BOARD 16 6 Nov 1997 TOSHIBA B 230V ...
Page 249: ...Nov 1997 TOSHIBA 16 7 4560 4570 PC BOARD 16 7 PS HVT ...
Page 342: ...4560 4570 RADF 18 84 Nov 1997 TOSHIBA 18 16 2 Control PC board circuit PWA F LGC 770 ...
Page 343: ...Nov 1997 TOSHIBA 18 85 4560 4570 RADF 18 16 3 Harness connection ...