Printronix L1024, Maintenance Manual

Page: 364 / 372

D–2 Appendix D – Principles of Operation
Charging the OPC Drum
The main component of the printing system is the OPC (organic photoconductor) drum. It is a cylinder
with special properties. The material of the OPC is an insulator when in the dark and is conductive
when exposed to light.
Before beginning the process, the OPC drum must be electrically charged. Figure D–1 shows the
organization of the OPC drum charger. A single tungsten wire is centered in a metal channel over the
OPC drum. This channel has a wire grid between the lower open end of the channel and the material
of the drum. The air around the wire is ionized by the high negative potential, approximately –5000
volts, of the wire. The grid of the channel is maintained at a voltage “less negative” than the tungsten
wire, approximately –680 volts. This voltage differential controls the ions flying toward and past the
grid and onto the OPC drum. These ions set up a negative potential of approximately –700 volts on
the surface of the OPC drum as it rotates under the metal channel.
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Grid
OPC Drum Rotation
High Negative Potential
Less Negative Potential
Metal Channel
Tungsten Wire (Charge Corona)
OPC Drum Rotation
Figure D–1. Charging the OPC Drum