Ricoh FT4460, Service Manual, Page: 78 / 413

28 February 1989
ERASE LAMP TIMING
4.1.1 Lead Edge Erase
The entire line of LEDs turns on when the main motor turns on. They stay on
until the erase margin slightly overlaps the lead edge of the original image
area on the drum (Lead Edge Erase Margin). This prevents the toner density
sensor pattern from being developed every copy cycle and the shadow of the
original edge from being developed on the paper. The width of the lead edge
erase margin can be adjusted using SP Mode #41.
During image density detection cycles (once every ten cycles), a block of
erase lamps turns off long enough for the sensor pattern to be developed.
The entire line of LEDs turns on when the residual voltage is being detected
(Vr. correction).
4.1.2 Side Erase
Based on the paper size and the reproduction ratio, the LEDs turn on in pairs
(one on either side) to discharge the drum potential on both sides. This
reduces toner consumption and drum cleaning load. The side erase margin is
overlapped to the size of the paper to prevent both sides of the original from
being developed on the copy image.
In A3 size, no erase lamps are turned on and side erase is done by the end
block of the charge unit. (This does not apply to 11” x 17”, as it is narrower
than A3 and does use the LEDs for side erase.)
Erase lamp “on” timing depends on the combination of cassette data and the
reproduction ratio data. In case of full size and enlargement copying, erase is
made only by cassette data. In reduction, erase is made by cassette data and
reproduction ratio data.
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