5.2 Setting A
NOTE
Setting A is sometimes needed when the following replacements
and adjustments are made:
Replacing the exposure glass (black-and-white pattern on the back of the original scale), xenon lamp, potential
sensor, or adjusting the reflectors (or mirrors) for uneven illumination
CAUTION
1. The target VL and VD are adjusted at the factory. Even after doing any of the
procedures above, you do not usually have to perform setting A. Read the OPC
potentials for the black and white areas of the PC-1 chart with service tool [4-03]. Only
when they are very different from the preceding values as a result of the above
procedures, perform setting A. Do not change the target VL and VD values too much.
2. Every 1,000K copies use the PC-1 chart in the same way as the above.
3. Install all exterior covers when doing setting A. External light might affect the OPC
potential.
4. Do not continue free run (more than 100 copies) from the [4-01] screen. Toner
density in the cleaning unit will be reduced and the cleaning carrier’s power to attract
toner will lower. This may cause toner scattering from the cleaning unit. This problem
occurs also when:
1) Making more than 100 free run copies from the [4-01] or [4-02] screen.
2) Turning on the main motor for more than 5 minutes using the I/O test mode in the
service tools.
3) Making more than 100 white copies.
If dirty copy images appear due to toner scattering from the cleaning unit, perform the
cleaning carrier forming with service tool [3-04].
The process control of this machine runs based on the VL and VD data set in the service tool [4-01]
screen (Target VD and VL). However, the data varies from one machine to another. This is due to
stains and/or variations in reflectivity of reflectors, exposure glass, mirrors, etc. (distortions of the
light path). For example, if the position of the light reflectors are changed, the ratio of light density
from the black pattern and from the white pattern varies. (If the OPC belt or flash power supply unit
is replaced, the OPC potential made by the light reflected from the original or the light density that
exposes the OPC surface might change. However, as the light density ratio from the black pattern
and from the white pattern does not change, the target VL and VD do not have to be changed.) To
compensate for variations between machines, setting A should be performed.
To do setting A, use the PC-1 chart. It has a uniform and steady density of black and white areas.
On the service tool [4-03] screen, the potential of the OPC made by exposing an original on the
exposure glass can be known. (This data is usually used to determine the development bias level
for the auto image density mode.) When the PC-1 chart is placed on the exposure glass, the
uniform and steady black and white areas of the chart should make the same potential on the OPC
and the data on the [4-03] screen should be the same from one machine to another. Adjust the grid
and flash setting on the [4-01] screen, so the white area of the PC-1 chart makes a potential of
--125 volts on the OPC and the black one makes a potential of --710 volts. Under this setting of the
grid and flash output, the values of the actual VL and VD (measured values) on the [4-01] screen
show those of the target VL and VD.
Setting A 1 July 1994
5-4
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