Canon NP6218 Service Manual page 174

CHAPTER 6 FIXING SYSTEM
The fixing film sensor (PS9) is used to detect the position of the fixing film and found
at the end of the film.
The rear (sensor side) of the fixing film is provided with a cut as shown in Figure 6-
106 so that the fixing film sensor continuously goes on and off.
Normally, the on and off periods of the sensor are identical as long as the fixing film
remains centered.
If the film starts to become displaced toward the rear, however, the on period
becomes longer; the off period becomes longer if the film starts to be displaced toward
the front. (See Figure 6-107)
The DC controller monitors the on and off periods of the sensor and computes the
difference to correct the position of the fixing film.
6-8
(unit: mm)
Fixing film
(rear)
Tension roller
Drive roller
Figure 6-106
ON
Normal
OFF
ON
(rear)
OFF
ON
(front)
OFF
Figure 6-107
COPYRIGHT © 1997 CANON INC.
5
(front)
OFF
ON
CANON NP6218 REV. 0 MAY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)