Fusing Lamp Control Circuit - Ricoh Robin Service Manual

IMAGE FUSING

10.3 FUSING LAMP CONTROL CIRCUIT

Main Board (PCB1)
B
CN107-1
Zero
R112
Cross
+5V
R110
CPU
R109 R111
I/O
IC114
+24V
AC Power
Zero Cross
Trigger Pulse
Lamp Power
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 SP29, 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.
CN118-2, 3
Fusing
+5V
Thermistor
TP102
(HET)
CN118-1, 4
+24V
IC104
R107
8
5
R108
7
CN114-8
6
4
C106
Q101
24V
CN114-4
0V
Trigger Pulse
C
CN114-6
CN114-7
A
B
C
D
2-56
AC Drive Board (PCB2)
R412
CN401-1
PC402
TRC402
CN401-5
CN401-3
CN401-2
24 June 1994
T402
T405
Thermo-
switch
Fusing
Lamp
D
T406
A
CR402
AC115V
AC220V
AC240V
RA401 T407
R414
RA401
Power Relay