Figure 3-6 Developer Housing - Xerox 7700DX - Phaser Color Laser Printer Service Manual

Bead Carryout (BCO)
The ATC Sensor magnetically measures the ratio of toner particles to
developer carrier beads, not the volume. Under a combination of rare
circumstances and component tolerances, it is possible fo rthe carrier beads
to be pulled from the Developer during printing; this is called bead carryout or
BCO.
The Engine Control Board will only auger in the amount of toner to achieve
the desired ratio with the remaining carrier beads. If beads are being carried
out, then less and less toner will be augered into the Developer Housing. no
error message will necessarily be displayed. Printing of that primary color will
get progressively lighter and lighter. In such a case, the Developer Housing
must be replaced.
The Developer/Toner mix should fill the Developer
about to the shafts of the two Augers.

Figure 3-6 Developer Housing

Print Cartridges
The four Print Cartridges in the printer are rarely the cause of any print quality
problems. A Print Cartridge is a fairly simple component; there is very little
that can go wrong with it. Realistically, the only reason a Print Cartridge
should be replaced is for a repeating defect to the cartridge's photoconductive
drum.
Phaser 7700 Color Laser Printer Service Manual
Opened Developer Housing
Developer/Toner should
adhere to the Magnetic
Roller.
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