Fault In The Laser Scanner - Canon CP660 Service Manual

IV. FAULT IN THE LASER SCANNER
The laser scanner is checked for a fault by the D-CPU (IC201) by monitoring the BD*
signal by way of the GA. It then stops the laser scanner motor if the cycle of the BD* sig-
nals fails to be a specific cycle (Note 1) or the cycle of the BD* signals deviates from a
specific cycle (Note 2). At the same time, the D-CPU forces the laser to turn on to mon-
itor the photodiode inside the scanner unit to identify a fault in the laser or the laser scan-
ner motor; at the end, it communicates the result to the printer board*
detected momentarily, the D-CPU identifies it as a BD error.
If the motor drive signal is continuously applied while the laser scanner motor is
locked, damage to the motor can occur. To prevent such a problem, the printer unit is
equipped with a lock detection circuit which forces off the motor as an additional protec-
tive mechanism.
The lock detection circuit assumes that the scanner is locked if the VUP* signal and
the PLUP* signal continue for 5 sec after the laser scanner motor starts to rotate (during
initial drive); upon detection, the laser scanner motor drive signal (SCND) is made to go
'0' and, at the same time, charges are stored in the error memory capacitor (C286). Once
charges are stored in the capacitor, the SCND signal will be cut off, stopping the laser
scanner motor drive. (See Note 3.)
1
* Reader controller PCB (when making prints with the reader unit installed).
Note:
1. If the cycle of the BD signals fails to be a specific cycle 7 sec after the scanner
motor starts to rotate (during initial drive).
2. If BDRDY is "false" for 2.5 sec or more after the scanner motor has reached its spe-
cific speed (after BDRDY has been written to the internal register of the GA).
3. The error memory capacitor (C286) is a protective mechanism preventing continu-
ous application of the scanner motor drive signal. The error of the lock detection cir-
cuit is initialized in 10 sec or so. The SCNON signal also forces the capacitor to dis-
charge, thereby initializing the error.
Reference:
E100: Fault in the laser.
E110: Fault in the laser scanner motor, or a BD fault.
COPYRIGHT © 1999 CANON INC.
Download free service manual at http://printer1.blogspot.com
CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 3 LASER EXPOSURE SYSTEM
1
. If BDERR is
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