Ricoh FT5233 Service Manual page 39

PROCESS CONTROL 12 February 1992
1.4 V PATTERN CONTROL
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1.4.1 Overview
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D Sensor Pattern
V Pattern
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DC
PSU
Main
Board
(V)
V Sensor
Drum
Potential
Exposure lamp voltage (V)
Dirty optics or deterioration of the exposure lamp decreases the intensity of
the light that reaches the drum via the optics cavity. As more copies are
made during the drum's life, the photo conductive layer gets worn and drum
sensitivity drops. The drum sensitivity also drops under low temperature
condition.
V pattern control is performed on this copier to prevent dirty backgrounds
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caused by the factors mentioned above. The V sensor is also used for V
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pattern control as well as for V pattern control.
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The V pattern (light gray) is located on the non-operator side of the bottom
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of the left scale bracket. When a copy job finishes in V pattern detection
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timing, the exposure lamp stays on for about 6 seconds while at the home
position. The V pattern is lit and a latent image of it is made on the drum.
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After this image is developed, its reflectivity is checked by the V sensor. The
CPU notes the strength of reflectivity, and if the reflected light is too weak,
the exposure lamp voltage is increased.
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