Image Transfer Current Timing - Ricoh Russian-C2a Service Manual

10 August, 2001

2.9.2 IMAGE TRANSFER CURRENT TIMING

There are two transfer current levels: low transfer current level and high transfer
current level. The image transfer procedure is as follows:
1. When the CPU receives the image writing start signal, the CPU instructs the
high voltage supply board to supply +10µA (low transfer current level) to the
roller. This prevents any positively charged toner on the drum surface from
transferring to the transfer roller.
2. At a certain time after the low transfer current has been supplied to the roller,
an appropriate current is applied to the roller to transfer the toner to the paper.
3. After the trailing edge of the paper has passed through the roller, transfer
current turns off. In multiple copy mode, the transfer current shifts again to the
low transfer current.
The transfer current (high transfer current level) depends on the paper feed station,
paper width, and the temperature in the machine.
Example: Temperature = 15°C ~ 24°C
Paper Width
A3/11" x 17",
A4/8 x 11"sideways
1/2
B4
A4/11" x 8 lengthwise,
1/2
A5/5 x 8 sidewise
1/2 1/2
A5/8 x 5 lengthwise
1/2 1/2
and less
The transfer current can be adjusted using SP2301, except for the low transfer
current.
Be careful when increasing the transfer current. This might cause a ghosting effect,
in which part of the image at the top of the page is repeated lower down the page
at a lower density. It may also damage the OPC drum in the worst case.
IMAGE TRANSFER AND PAPER SEPARATION
Paper Tray /
By-pass Tray Duplex (2nd Side)
(Normal)
14 µA
13 µA
13 µA
16 µA
2-59
By-pass Tray
(Thick) / 2nd
Paper Tray
(Special Paper)
10 µA 14 µA
12 µA 15 µA
16 µA 17 µA
16 µA 20 µA