Oce 3121 Technical & Service Manual page 228

Switching the exposure lamp ON and OFF
The exposure lamp is switched ON and OFF by the lamp ON signal (FLPWM).
The signal is from the DC control PBA.
The FLPWM signal is sent to the logic circuit together with the MPCLK (pulse
signals), generated by the power supply PBA. The logic circuit uses these two
signals to generate the signal for 'exposure lamp ON', thereby switching on the
scanning lamp.
Varying the Intensity
The FLPWM signal is a pulse signal. This is used to control the intensity of the
exposure lamp to a specific level by varying the duty ratio. This is based on the
results of the automatic shading correction as executed in service mode, and in
accordance with the output of the exposure lamp intensity sensor.
Detecting Errors
If the exposure lamp fails to switch ON, although the lamp ON signal has been
generated, the exposure lamp ON circuit detects the condition. The error de-
tection signal (PRTCT) is sent to the CPU.
In response, the CPU generates the exposure lamp OFF signal (FLOFF). The
CPU does not wait for a command from the DC controller.
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