Exposure Lamp Control - Ricoh FT5540 Service Manual

3.2 EXPOSURE LAMP CONTROL

After the Start key is pressed, the main PCB sends the exposure lamp trigger signal [C] to
CN501-6 on the ac drive board. The width of the lamp trigger pulse is based on the setting of
SP mode #48 and on the zero-cross signal [B] from the ac drive board. This lamp trigger
pulse activates the triac on the ac drive board, which provides exposure lamp power [D] from
the 100-volt ac line [A].
The power supplied to the exposure lamp is also provided to the lamp monitor circuit, which
rectifies it and supplies it to the Sub CPU analog port [E]. This allows fine tuning of the trigger
pulse width and ensures accurate circuit operation. The lamp monitor signal is also monitored
by a timer circuit in the main board. Should this signal stay active for longer than 15 seconds,
the main board energizes relay RA on the ac drive board. This causes relay RA1 to
de-energize, removing power from the exposure lamp. The copier stops and SC #12 is
displayed.
Use SP mode #51 to display lamp voltage in the guidance display.
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31 August 1989