DRUM UNIT 15 February 2006
6-62
Development Bias, Bias Grid, and LD Adjustment
Development Bias (Vb)
First, the development bias that will be used for copying (Vb) is determined by
measuring the potential of a pattern made on the drum using a fixed grid voltage,
development bias, and laser power.
1. The drum motor starts.
2. The grid voltage, development bias, and laser power are set to the default
values that would be used if process control was disabled. These are as
follows:
• Development bias is set to the value stored in SP2201-001
• Grid voltage is set to the value stored in SP2001-001
• Laser power is set to a fixed value
3. A VL pattern is made on the drum, and VL is measured. The target value of VL
is –130V.
VL: Potential measured after exposing a white pattern
4. Vb is adjusted to a value that is calculated to bring the value of VL to –130V.
There are no limitations on the amount of change that can be made to Vb.
Grid Voltage (Vg)
Then, the machine determines the corona grid voltage (Vg) that will be used during
copying. This is done as follows:
1. A Vd pattern is exposed on the drum (if developed with toner, this will be
black).
Vd: Drum potential in black areas after exposure.
2. The potential sensor reads the potential, Vd, from this pattern.
3. Vd should be –800 ± 10V. If it is within this range, the current value of Vg will
be used for copying.
• If it is not, -(Vd + 800)V is added to Vg, and the process starts again from
step 1.
4. If Vd cannot be adjusted to this standard within 5 attempts, Vg is fixed to –
1,000V and SC312 (Potential Sensor Calibration Error 3) is logged.
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