2-24 Phaser 7750 Printer Service Manual
ATC Sensors
The ATC sensor is a part of the developer housing. It provides an indication of the
concentration of toner relative to the carrier beads contained in the developer housing.
Generally speaking, higher concentrations of toner are more easily developed,
because they have less triboelectric bond to the carrier beads. Lower concentrations
have a higher attraction to the carrier beads, and therefore require higher charge to
develop out.
The ATC sensor provides its information to the process controls.
The "Tone Up/Down" test in diagnostics compares a corrected target value to the ATC
sensor value on each individual developer. If the corrected target value is within +/-30
of the sensor value then printer logic assumes toner concentration is correct. If the
corrected target value is greater than 30 units above the sensor value, printer logic
detects that the toner concentration is lighter than the target value and adds toner to
the developer.
If the test values all equal the results shown below, the test has not detected any
problems.
<Tone Up/Down>
Result = 0 Status = 0
ATC Sensor Fail = None
ATC Limit Warn = None
ATC Change Warn = None
If the ATC sensor fails, possible causes are:
■ The sensor connection is bad, try reseating the connector.
■ The sensor is defective.
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