Canon 1000 Service Manual page 133

b. Initial Potential Control
Under this control, ideal grid and developing biases are determined as shown in Figure 3-507. The grid
bias (Vg) of the primary charging assembly is set to two different voltages as in Figure 3-508 to measure the
dark area potential (Vd: 00 activation of laser) and the light area potential (VL: full activation of laser).
Power switch turned ON
Video signals set to 00H and FFH
Vg set to -300 V; Vd and VL measured
Vg set to -700V; Vd and VL measured
Grid bias (Vg) and developing bias (Vdc) computed
so as to obtain selected contrast potential
Start key ON
Figure 3-507
Subsequent copying operations are executed using the grid bias and the developing bias determined as
discussed; the timing of measurement is as follows:
Power switch ON
Drum motor
Pre-exposure lamp
Potential measurement
Lasers for Y,M,C,Bk
Grid bias
Developing bias
COPYRIGHT © 2001 CANON INC.
Vg-Vd/VL characteristic shown
in Figure 3-508 computed
based on measurements
Contrast potential computed
by PASCAL
Drum full rotation 1/2 rotation 1/2 rotation 1/2 rotation 1/2 rotation 1/2 rotation 1/2 rotation 1/2 rotation
VL VL VD
FF activation 00 activation
-300V
-200V
Figure 3-509
CANON CLC1000/1000S/3100 REV.2 MAY 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)
3. OPERATION AND TIMING
Potential
(negative)
Vd1
VL1
Vg1(-300V)
Figure 3-508
WMUPR
VD VL VL VD
FF activation 00 activation
-700V
-500V
Vd
Vd2
VL2 VL
Vg2(-700V)
VD
3-89