Ricoh Robin Service Manual page 49

DEVELOPMENT
5.4.4 Drum Residual Voltage (Vr) Correction Factor
During the drum's life, drum residual voltage (Vr) will gradually increase. The
Vr correction compensates for the residual voltage on the drum. The Vr
correction is done every 1,000 copies. The following table shows how the
development bias voltage changes depending on the Vr ratio.
Vr ratio (L) (%) (SP67) Change of bias voltage (volts)
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 correction pattern
Vsg: ID sensor output for bare drum
When the Vr correction is made (every 1,000 copies), all blocks of erase
lamps turn on and the development bias becomes 0 volt to develop the Vr
pattern.
±0
–40
–80
–120
–160
2-30
24 June 1994