Photosensitive Drum; Drum Sensitivity - HP LaserJet II Serie Manual De Instrucciones

HP 33440/HP 33449 COMBINED SERVICE MANUAL
Photosensitive Drum
The photosensitive drum-the core of the image formation system-has special propetiies which
allow an image to be formed on its surface and then transferred to paper. The drum is an
efiruded aluminum cylinder which is coated with a non-toxic layer of organic photoconductive
material (OPC). The aluminum base of the drum is electridly connected to ground.
The OPC material has propetiies similar to a photodiode. It becomes electridly conductive (in
one direction only) when exposed to light. Negative charges deposited on the surface of the drum
conduct to the aluminum (zero potential) base of the drum when exposed to light. Areas of the
drum not exposed to fight remain nonconductive and retain the initial charge.
caution
Do not expose the drum to direct sunlight or any other bright tight source;
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u
permanent damage to the drum could occur.
Drum Sensitivity
Because dl drums cannot be manufactured to the exact same sensitivity levels, they are tested at
the factory and given a rating of high, medium, or low sensitivi~ (see Table 5-l). Depending on
this rating, tibs are placed on the mrtridge which enable printer micro~tches which, in turn,
control bser power output to adjust for the drum's sensitivi~ level. These microswitches dso
indicate whether or not the EP-S Cartridge is instiled.
Table 5-1. Drum Sensitivity Tab Settings
-.
D= Sensitivity.
Csms
1 CSENS 2
High
L
L
Medium
L
H
Low
H
L
Cartridge not Instiled H
H
IL = Switch Activated
I
High-Voltage
Power Supply
Figure 5-3. Photosensitive Drum
5-5