Specifications

11.4 FUSING LAMP CONTROL CIRCUIT
The main board monitors the fusing temperature through a thermistor. It also
uses the zero cross signal generated by the dc power supply board to
accurately control the applied power.
Normally, the voltage applied to the lamp is a full ac waveform. However,
through SP mode #29, fusing power can be phase controlled. (Normally,
phase control is used only if the customer has a problem with electrical noise
or interference.)
When the main switch is turned on, the main board starts to output a trigger
pulse [C], which has the same timing as the zero cross signal [B], to the ac
drive board. This trigger pulse allows maximum ac power to be applied to the
fusing lamp. When the operating temperature is reached, the CPU stops
outputting the trigger pulse (trigger goes HIGH) and the fusing lamp turns off.
CN108-1
+24V
Trigger Pulse
R118 R117
R116
+5V
IC121
+24V
+5V
CN122-1
CN122-14
CN122-10
CN122-12
CN122-13
CN401-3
CN401-2
CN401-6
CN401-1
CN122-2
R127
Zero
Cross
CPU
I/O
IC124
TP107
(HT)
C162
R124
R125
24V
0V
Fusing
Thermistor
R414
R412
TRC402
CR402
RA401
Power Relay
Thermo-
fuse
Fusing
Lamp
AC115V
AC220V
AC240V
T402
T405
T406
T407
PC402
RA401
Main Board (PCB1)
AC Drive Board (PCB2)
Q110
B
C
D
A
5
8
7
6
4
AC Power
Zero Cross
A
Trigger Pulse
Lamp Power
B
C
D
1 December 1990
2-73