Protection Mechanism - Canon NP6330 Service Manual

C. Protection Mechanism
The copier uses the following three to prevent malfunction of its fixing heater:
• Signal from the thermistor
• Signal from the SSR
• Thermal switch
a. Protection with Signal from the Thermistor
The DC controller PCB monitors the voltage of the thermistor (TH1) and indicates a
self diagnosis code in response to overheating.
If the temperature of the fixing roller reaches 220°C (detected by the thermistor TH1),
'E001' will be indicated on the control panel and the copying operation will be stopped.
If the temperature of the fixing roller as detected by the thermistor (TH1) exceeds
220°C for some reason, the error auto power-off signal (PWOFF*) is generated to turn
off the power switch.
Table 6-202 shows the relation between the surface temperature of fixing roller and
the voltage of thermistor. (The voltage is theory value.)
Temperature of the
fixing roller (°C)
0
10
20
30
40
50
60
70
80
90
100
110
COPYRIGHT © 1997 CANON INC.
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Voltage of the
thermister
4.98
4.97
4.95
4.92
4.87
4.80
4.70
4.56
4.39
4.16
3.89
3.58
Table 6-202
CANON NP6330 REV.0 MAY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 6 FIXING SYSTEM
Temperature of the
fixing roller (°C)
120
130
140
150
160
170
180
190
200
210
220
Voltage of the
thermister
3.23
2.87
2.51
2.16
1.84
1.56
1.30
1.09
0.91
0.75
0.63
6-5