Bias For Id Sensing - Ricoh FT7770 Service Manual

Bias for ID Sensing

7.
In order to develop the ID sensor pattern consistently, the CPU applies a
fixed bias level to the development roller at the end of each copy cycle.
The fixed base bias is 410 volts and it is affected by drum cavity tempera-
ture and drum rest time.
The CPU applies the ID sensor bias to the development roller about 250 mil-
liseconds after the scanner overshoots the home position. Just after the sen-
sor pattern is developed, the CPU changes the bias output to the level se-
lected by the auto ID sensor or the operator.
The ID sensor bias can be changed to adjust the overall image density by set-
ting various combinations of the SP memory frames.
Base Voltage
*410 v
350 v
470 v
500 v
The factory setting is 410 V.
When in a reduction mode of less than 74%, +30 volts is added to the ID sen-
bias.
sor
SP1O-1 SP1O-2
Reset
Reset
Set Reset
Reset Set
Set Set
2-37
30
April, '89