Ricoh FT5034 Service Manual page 47

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 on every
copy cycle and prevents the edge of the original from appearing on the copy
image. The width of the lead edge blank margin can be adjusted with DIP
SW102-5, 6 and -7 on the main board.
During image density detection cycles (once every ten cycles), the center block
of erase lamps turns off long enough for the sensor pattern to be developed.
2. Side Erase
Based on the paper size and on the reproduction ratio, the LEDs turn on in pairs
(one on each side) to discharge the drum potential on both sides. For A3
copying, the drum potential is not erased by the erase lamp but by the charge
corona end blocks.
3. Erase Lamp
Erase lamp segments are turned on and off based on the cassette data and
reproduction ratio data as shown on the next page.
For full size and enlargement copying, on/off switching is based only on cassette
data. For reduction copying, it is based on an OR circuit between cassette data
and reproduction ratio data.
32 LEDs
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