Ricoh B156 Service Manual page 384

development bias values are fine-tuned to correct for any changes in the machine
or temperature/humidity since the last full process control.
This step always has to be done when installing a new development unit. The toner
amount carried by a development roller varies with each unit. (The toner amount
used for a certain development bias is not the same.) Black development bias
initialization (step 3) has to be done more often, because tests have shown that
process control errors occur more often if this is not done.
Step 3. Initializing K Development Bias
Similar to the process for color development bias. M/A must be 0.65 mg/cm
areas of maximum image density. Range: 0.40 to 2.0 mg/cm
Step 4. Fine-tuning the YMCK Development Biases
The machine makes another solid pattern
Steps 2 and 3 for determining VB (development bias) are not done every process
control (see the table: When is the process control done?). Because of this, the
solid area density, based on the VB obtained during initialization, may change as a
result of changes inside the machine after a period of use, or because of
environmental changes. To suppress these fluctuations, this step fine-tunes VB at
regular intervals, or if the environmental conditions change.
The machine adjusts the development bias based on these results.
Step 5. Charge Grid Voltage Adjustment
The machine makes a very low image density pattern (20x25 mm), which consists
of a replacing 3 x 3 matrix of pixels on the OPC belt. Two of these pixels are of
high intensity (dark), and the others are at zero intensity (LD off, white). The two
high intensity pixels are close together.
0
240 240
0
This is only to give you a rough idea - the exact pixel densities used by this
machine are not shown here.
The net effect is to have two dark pixels surrounded by white pixels on all sides,
repeated all over the paper.
If there is a difference between the target M/A and the detected M/A, the grid
voltage is adjusted.
Step 6. Resetting the Process Control Interval Counter
The counter is in the NVRAM on the controller board, and is reset after process
control. The counter is not reset after black development unit or black toner
cartridge replacement. This is because only a few of the process control steps are
done after replacing these components.
B156/B220
CÓPIA NÃO CONTROLADA
0 0
0
0 0
CÓPIA NÃO CONTROLADA
6-18
PROCESS CONTROL
2
for
2
SM