Ricoh A-P4, Service Manual

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The machine detects the toner concentration using Vref, Vt (10), Vtp, and Vtp1. If the toner concentration
is still too low, the toner supply motor remains on for another 10 seconds while the machine checks Vt. If
toner concentration is judged to be at the standard level, then the toner near end/end condition is cancelled
and K (toner supply coefficient) is reset. If toner concentration has not reached the standard level, the toner
supply motor rotates continuously until it does (maximum motor on time is 16 seconds) and then it will switch
off.
Toner Supply with Abnormal Sensors
The TD sensor is checked every copy. If the readings from the TD sensor become abnormal during a copy
job, the machine holds the GAIN factor constant (GAIN is normally calculated from TD sensor readings)
to allow toner supply to vary with only pixel count for the rest of the copy job. Then at the end of the copy
job, an SC code is generated and the machine must be repaired.
The ID sensor is checked every 10 copies. If readings become abnormal, an SC code is generated and
the machine must be repaired. If this happens during a copy job, Vref is not changed, the copy job is
allowed to finish, and then the SC code is generated.
If spare parts are not available, the technician can use SP2-208-1 (Toner Supply Mode) to temporarily
put the machine in image pixel count mode. (See Section 5 Service Tables.)
6. Details
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