Toshiba e-STUDIO4500c Service Manual page 727

August, 2006
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Here is a general description of the copy process in the black PCU. These
mechanisms are identical in each PCU (Y, C, M, K).
1. DRUM CHARGE
In the dark, the charge roller gives a negative charge to the drum. The charge
stays on the surface of the drum because the OPC layer has a high electrical
resistance in the dark.
2. EXPOSURE
A xenon lamp exposes the original. Light reflected from the original passes to
the CCD, where it is converted into an analog data signal. This data is
converted to a digital signal, processed, and stored in the memory. At the time
of printing, the data is taken from the memory and sent to the laser diode. For
multi-copy runs, the original is scanned once and stored in a temporary file on
the hard disk.
3. LASER EXPOSURE
The processed image data from the scanned original is taken from the hard
disk and two laser beams send it to the drum. The lasers write an electrostatic
latent image on the drum surface. The amount of charge remaining as a latent
image on the drum depends on the laser beam pulse duration and the laser
power (controlled by the BICU).
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K
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COPY PROCESS OVERVIEW
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