Ricoh Robin Service Manual page 27

DRUM CHARGE
2.5.2 Drum Residual Voltage (Vr) Correction Factor
Vr ratio (L) (%) (SP67)
100 to 84
83 to 58
57 to 41
40 to 28
27 to 0
L = Vrp/Vsg x 100 (%)
Vrp: ID sensor output for Vr pattern
Vsg: ID sensor output for bare drum
During the drum's life, drum residual voltage (Vr) may gradually increase. Vr
correction compensates for the residual voltage on the drum. The Vr
correction is done every 1000 copies. The CPU increases the development
bias voltage and the grid voltage. The above table shows how the grid
voltage changes depending on the Vr ratio.
2.5.3 Auto Image Density Level Factor (SP34)
Auto image density level
Normal
Darker
Lighter
The grid voltage and the exposure lamp voltage are constant regardless of
the output from the auto image density sensor. Only the development bias
voltage varies depending on the output from the auto image density sensor.
But only when the auto image density level data in SP34 is set to darker, the
grid voltage is changed –40 volts as shown in the above table. When it is set
to lighter, the grid voltage does not change. However, the development bias
voltage is corrected.
Change of grid voltage (volts)
±0
–40
–80
–120
–160
Data (SP34)
0 *
1
2
2-8
24 June 1994
Change of grid voltage (volts)
±0
–40
±0
* Factory setting