Ricoh FW830, Service Manual

Page: 29 / 227

3.4 EXPOSURE LAMP CONTROL
The lamp regulator receives 100 volts ac at CN1-1 and CN1-2. It also
re5 volts, which is used in the lamp regulator’s control circuit, from
the main board at CN2-1. The control signal, which is a pulse width
modulated (PWM) signal, is received at CN2-2. The PWM signal has a period
(T) of 1 millisecond and a duty of 15% to 100%.
The basic light intensity level is determined either by the image density
selected from the operation panel (manual ID control) or by the original’s
background level as sensed by the ADS. The CPU uses the light sensor to
monitor the actual light intensity. The light sensor directly senses the lamp’s
light output and feeds a light intensity signal back to the main board. This
feedback allows the CPU to compensate for variations in light intensity due to
the lamp’s age or temperature.
[L1]
CN3-1
CN3-2
CN3-4
CN3-5
CN1-1
CN1-2
CN2-1
CN2-2
+5V
PWM
Lamp OFF (+5V)
Lamp ON (GND)
T
T = 1.0 ms
Duty = 15% to 100%
LAMP
REGULATOR
Exp. Lamp
[PCB4]
CN2-2
EXPOSURE 31 December 1992
2-10