COPYRIGHT © 1999 CANON INC. CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)b. Open Circuit in the Fixing Heater (E004)At the start of temperature control, the printer unit drives the upper fixing heater andthe lower fixing heater, one at a time to check the FXSTS signal for an open circuit in thefixing heaters.The fixing assembly error detection circuit detects AC current flowing through the fix-ing heater. If AC current is absent, the M-CPU on the DC controller PCB will assume thecondition as an open circuit in the fixing heater, stopping the drive to the fixing heater andcommunicating the fact to the printer board*1 as a fault in the fixing assembly.The AC current to the upper/lower fixing heater is checked in reference to the voltageinduced at T101. The voltage occurring at T101 is monitored by pin No. 10 of IC102. If theupper/lower fixing heater has an open circuit or if the upper thermal switch opens, AC cur-rent stops flowing and the output of pin No. 13 of IC102 goes ‘1’. As a result, the outputof pin No. 14 of IC102 will be ‘1’, and the fixing heater status detection signal (FXSTS)will go ‘0’.If AC current is flowing, on the other hand, the FXSTS signal alternates between ‘1’and ‘0’ at specific intervals, allowing the M-CPU to use the FXSTS signal to detect anopen circuit in the fixing heater.*1 Reader controller PCB (when making prints with the reader unit installed).CHAPTER 6 FIXING SYSTEM6-8Download free service manual at http://printer1.blogspot.com
