Panasonic Panafax UF-4000, Service Manual

Page: 198 / 284

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3. Fuser Temperature Control Circuit
The fuser temperature is controlled by IC1 on the SC PC Board, which contains A/D (Analog/Digital)
converters ANI0 to ANI7. The Fuser Temperature Control Circuit uses A/D converter, ANI1. When the
PC001 drive current is transmitted from the SC PC Board to the LVPS(PSU), the Fuser Lamp turns ON.
IC23 is a comparator with open output at pins 1 and 7 and is used as an abnormal temperature detection
circuit. IC23, pin 1, has a high impedance when Q35 is activated, turning ON the Fuser Lamp.
An abnormal temperature is detected when the VTH voltage level becomes higher than V+, forcing IC23,
pin 1 Low and deactivating Q35.
Abnormally low and high temperatures, as well as Thermistor release status, are detected by IC1 (CPU)
programming.
GND
GND
Q35
3
2
R188
R195
3
IC23
4
1
2
2
2
R189
GND
R184
R194
C156
R303
+5v
+24V
+3.3V
+3.3V
+3.3V
D13
C202
GND
PC001
1
2
6
4
+24v
R221
Thermistor
SNSE PCB
PSU (LVPS)
pSSRA
8
1
GND
Q34
3
1
Q32
3
1
79
SC PCB
2
1
CN7
TH2
D12
TH2
11
CN4
11
CN103
Fuser Temperature Control Circuit Diagram
(ANI1)
IC1
CPU
R199
R190
R191
IC3
SHINE