Bias For Id Sensing - Ricoh FT4430 Service Manual

BIAS FOR ID SENSING

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Bias
6 0 0
500
400
300
!
200
100
To develop the ID sensor pattern consistently, the CPU applies a fixed base
bias level to the development roller at the beginning of each copy cycle. The
fixed base bias is 470 volts (SP Mode data selectable) after ten copies; prior
to which, it is affected by drum cavity temperature and drum rest time.
The CPU applies the ID sensor bias to the development roller about 1.12
seconds after the Start key is pressed. Just after the sensor pattern is
developed, the CPU changes the bias output to the level selected by auto ID
sensor or the operator for image development. The bias output remains at
this level until 0.22 second after the scanner starts returning.
The ID sensor bias can be changed to adjust the overall image density by SP
Mode # 33 as follows:
ID Sensor Bias (SP Mode # 33)
Data
O .
1 . .
2 . .
3 .
Normally the data of SP Mode # 33 is "O" (factory preset).
Bias change Signal ( from Optics Board)
I
t
for ID Sens'or Pattern
( Fixed Bias)
Drum Temp = 30"C
Rest Time = Over 2hours
Auto ID Input = 3V
Base Bias
470V
440V
500V
530V
for 'Image
( S e l e c t e d B i a s )
for Image
2-31
16 April '88
I