Canon NP6251 Service Manual page 117

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ON
Measurement by
potential sensor
Scanning lamp
Primary charging
a. Controlling the Primary Charging Current
The light area potential (V
a standard current (stored in ROM) to the primary charging assembly and using the
potential sensor.
The DC controller PCB compares the measurement of the drum surface potential
and the target potential; if there is a discrepancy, the primary charging level control signal
(HVTPC) from the DC controller PCB is corrected, and the potential is measured once
again.
Caution:
If the measurement is not within the tolerance of the target value after eight tries,
'1' is indicated to 'PLMT' (upper limit flag of primary current) in service mode (*1*;
display mode).
b. Controlling the Intensity of the Scanning Lamp
The light area potential (V
by applying a reference activation voltage (stored in ROM) on the scanning lamp.
The scanning lamp illuminates the standard white plate, and the light reflected by it
is directed to the drum.
The surface potential of the area on the drum exposed to the light is measured by
the potential sensor, and the measurement is sent to the DC controller PCB.
The DC controller PCB compares the measurement against the target value; if there
is a discrepancy, the intensity adjustment signal (LINT) from the DC controller PCB is
corrected, and the potential is measured once again.
COPYRIGHT © 1997 CANON INC.
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INTR CNTR1
V V V V
D D D
Reference Correction
current current
Figure 4-102
) for the first time after power-on is measured by sending
D
) is measured for the first time after power-on is measured
L
CANON NP6350/NP6251 REV. 0 JULY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 4 IMAGE FORMATION SYSTEM
CNTR2
V V V V V
D D L1 L1 L1 L1
Reference
voltage
Correction voltage
Last current
To SCFW or
AER
V V
L1 L2
Last current
4-3