Development Bias - Gestetner B003 Service Manual

6.9.4 DEVELOPMENT BIAS

Mechanism
In a negative-positive development
system, black areas of the latent image
are at a low negative charge (about –
150 V) and white areas are at a high
negative charge (about –950 V).
To attract negatively charged toner to
the black areas of the latent image on
the drum, the high voltage supply board
[A] applies a bias of –600 volts to the
development roller throughout the image
development process. The bias is
applied to the development roller shaft
[B] through the bias terminal spring [C]
and bias terminal [D].
The development bias voltage (-600 V) can be adjusted with SP2-201
(Development Bias).
Correction for paper width and thickness (by-pass tray only)
The by-pass tray can be used for non-standard paper narrow than sizes accepted
by the paper trays. Thicker paper, OHP sheets, etc. can also be loaded in the by-
pass tray but adjustments must be performed with the SP modes listed below in
order to avoid jams and misfeeds.
SP Mode
SP2-201-1 Development Bias
SP2-309-1 Paper Lower Width [a]
SP2-309-2 Paper Upper Width [b]
SP2-914-3
Process Control Setting (Bγ)
SP2-914-4
Process Control Setting (Bδ)
The way that these SP modes are used is shown below.
0 m m
Default: 150 mm
Voltage:
SP2-201-1 + SP2-914-3
Default: -600+250 V
For example, with the default settings, if the paper width fed from the by-pass tray
is 200 mm, the development bias voltage will be –600 + 50 V.
SM
[B]
SP Name
Width 216 - 297 mm
Width limit: 150 mm
Width limit: 216 mm
Adjust 10V/step
Adjust 10V/step
SP 2-309-1
Default: 216 mm
Voltage:
SP2-201-1 + SP2-914-4
Default: -600+50 V
6-49
DEVELOPMENT
[D]
SP 2-309-2
2 9 7 m m
Voltage:
SP2-201-1
Default: -600 V
B003/B004/B006/B007
[A]
[C]
B004D404.WMF
B004D508.WMF