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CHAPTER 2
IV. IMAGE FORMATION SYSTEM
A. Outline
The image formation system is the central hub of the printer, and consists of the photosensitive
drum, developing unit and charging roller etc.
When the PRINT signal (/PRNT) is sent from the video controller to the DC controller, the DC
controller drives the main motor to rotate the photosensitive drum with the laser diode, devel-
oping cylinder, primary charging roller, and transfer charging roller.
The primary charging roller uniformly applies a negative charge on the surface of the photo-
sensitive drum. To form a latent image on the photosensitive drum, the laser beam modulated
by the VIDEO signals (VDO, /VDO) is exposed to the photosensitive drum surface.
The latent image formed on the photosensitive drum is changed to a visible image by the toner
on the developing cylinder then transferred onto paper by the transfer charging roller. Residual
toner on the photosensitive drum surface is scraped off by the cleaning blade. The potential on
the drum is made uniform by the primary charging roller in preparation for the next latent
image.
The cartridge has a toner sensor that detects whether there is enough toner remaining and
whether the cartridge is installed.
If the toner in the cartridge becomes lower than the prescribed level or there is no cartridge
installed in the printer, the high-voltage power supply notifies the DC controller through the
TONER LEVEL signal.
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Troubleshooting
