Making Electrical - Canon LBP-2000 Service Manual

CHAPTER 4
B . Making Electrical Adjustments
1 . Adjusting the leading edge margin
VR101 (Figure 1-4-2) on the DC controller PCB is adjusted in the factory, not requiring adjust-
ment in the field. If you have replaced the DC controller PCB in the field, however, be sure to make
adjustments. If you have replaced the laser/scanner unit, on the other hand, make adjustments if
the leading edge margin is not 2.0 ±1.2 mm (check by making several test prints).
1) Remove the test print switch cover (Figure 1-4-2) at the rear of the Printer.
2) Set VR101 on the DC controller to the median index (±0), and place A4 or LTR paper in the
cassette. Then, press the test print switch to make several test prints.
3) Measure the distance (a) from the leading edge of the paper to the print pattern. (Figure 4-7-2)
4) Turn VR101 until the distance obtained in step 3 is 2.0 mm.
Turning VR101 clockwise moves the image in the direction of + (Figure 4-7-2), while turning it
counterclockwise moves it in the direction of -; a single index is a shift of about 1.7 mm.
5) For instance, if the average reading is 3.7 mm, turn VR101 clockwise in the direction of - to
make up for the difference of 1.7 mm. If the result is not as indicated, repeat steps 1) through
4).
CCW(– )
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Leading edge of paper
CW(+)
VR101
Figure 4-7-2
+
a
–