Specifications

5.4.3 Base Bias Voltage Adjustment Factor
Base Bias Adjustment
(Black toner: SP mode #37, Color Toner: SP mode #79)
Image Density
SP Data
(SP mode #37 or #79)
Change of
Base Bias Voltage
Normal 0 ±0 volts
Darkest 1 +40 volts
Darker 2 +20 volts
Lighter 3 –20 volts
Lightest 4 –40 volts
The base bias voltage can be changed in SP mode #37 for black toner or
#79 for color toner to adjust the image density level. The above table gives
the base bias voltage for each SP mode setting. This adjustment should be
done only when the exposure lamp voltage adjustment (SP mode #48) fails
to achieve the desired image density.
5.4.4 Vr Correction Factor
As the OPC drum is used, drum residual voltage (Vr) gradually increases. Vr
correction compensates for residual voltage on the drum. Vr correction is
done every 1,000 copies based on the data of the drum counter (SP mode
#69) and the Vr correction ratio (L) (SP mode #67). The following chart
shows how the bias voltage changes depending on the Vr correction ratio (L).
Vr Correction Factor
L Change of Bias Voltage
100 to 89 (%)
88 to 76 (%)
75 to 62 (%)
61 to 45 (%)
44 to 0 (%)
±0 (volts)
–40 (volts)
–80 (volts)
–120 (volts)
–160 (volts)
NOTE: L = Vrp/Vsg x100 (Vr Correction Ratio)
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 volts to develop the Vr
correction pattern.
1 December 1990
2-31