HP LASERJET ENTERPRISE MFP M725dn, Troubleshooting Manual

Page: 63 / 546

The DC controller detects the remaining toner level in a cartridge according to the TONER LEVEL
signal. The DC controller determines a cartridge low warning or cartridge end-of-life when the
toner level drops below a specified level and notifies the formatter.
●
Cartridge-life detection
The DC controller detects the cartridge life. The DC controller determines cartridge end-of-life and
notifies the formatter when the toner out.
Other image-formation functions
Drum discharge
The drum discharge is a feature to remove residual charge on the photosensitive drum surface for
preventing uneven image density. The laser-beam strikes the surface of the photosensitive drum to
remove the residual charge.
The drum discharge is performed during the LSTR period.
Figure 1-22 Drum discharge
Laser beam
Photosensitive drum
Transfer roller cleaning
The transfer roller cleaning is a feature to remove residual toner on the transfer roller surface to prevent
the back-side toner stain of the paper.
The residual toner reverse-transfers to the photosensitive drum by applying the reverse transfer bias to
the transfer roller. The residual toner is deposited in the toner collection box.
ENWW
Image-formation system
31