Exposure Lamp Control Circuit - Ricoh M5 Service Manual

6. Exposure Lamp Control Circuit

The control circuit shown above maintains a stable exposure lamp light output. The major compo-
nents are the main board, the exposure lamp stabilizer, and the exposure sensor.
– Image Density Level –
The Image Density keys are used to select five different levels of exposure light intensity. The key
input is sent to the CPU which then sends the lamp stabilizer a control signal consisting of a constant
1 millisecond pulse train (T).
power to the exposure lamp.
level.
— Exposure Lamp Stabilizer —
The exposure lamp stabilizer supplies drive power to the exposure lamp. The exposure lamp
receives +22 volts at
stabilizer
48 kHz, 250-volt ac signal which is used to drive the exposure lamp. The exposure lamp stabilizer
turns on the exposure lamp only when the control signal to CN 702-1 is LOW.
Exposure Sensor
1
f
The LOW (Tl) of each pulse commands the lamp stabilizer to supply
The length of the LOW varies according to the selected image density
CIW02-2.
An
internal switching circuit converts the
3 - 1 7
Main Boar-cl
I
25, 1985
May,
+22
volts to a