F. SSR Error Detection Circuit for the Fixing HeaterThe machine’s safety circuit for the fixing heater SSR uses the following signals sentto the DC controller PCB:1. Fixing main heater drive signal (MHRD)2. Main heater ON detection signal (MHOND)Figure 6-107 shows the main heater only, but the sub heater is controlled in the sameway.Heater ONThe CPU causes the SSRON signal to go ‘0’, and the MHRD signal goes ‘1’ to turnon the heater. At this time, the fixing assembly feeding unit detection signal (FFURLS),power switch ON detection signal (MSWD), and front door open detection signal (FDOD)are ‘0’.Heater OFFThe CPU causes the SSRON signal to go ‘1’, and the MHRD signal goes ‘0’ to turnoff the heater.SSR ErrorIf the main heater ON detection signal (MHOND) is ‘1’ when the CPU on the DCcontroller PCB is not generating the fixing main heater drive signal (MHRD), i.e., gatearray detection q, or if the main heater ON detection signal (MHOND) is ‘0’ when theCPU on the DC controller PCB is generating the fixing main heater drive signal (MHRD),i.e., CPU detection w, the DC controller will identify an error in SSR and issue an Ecode.To cut off the power to the AC circuit, the DC controller causes the power switch OFFsignal (PWOFF) to go ‘0’. When the power switch is turned off, the power to the heaterwill be cut off; however, since the power to the DC controller PCB is maintained for aspecific period of time, (see p. 7-9), the PWOFF signal is kept to prevent the relay insidethe power switch from turning on, thereby locking the power switch ON detection signal(MSWD) from the power supply PCB.Since the machine’s main heater ON detection signal (MHOND) will go ‘1’ under thefollowing conditions, the SSRON signal is kept ‘0’ so as to prevent detecting an SSRerror wrongly:1.When the fixing feeding unit is slid out (FFURLS=1).2.When the front door is opened (FDOD=1).3.When the power switch is turned off (MSWD=1).CHAPTER 6 FIXING SYSTEM6-12 COPYRIGHT © 1997 CANON INC. CANON NP6560/NP6360/NP6260 REV. 0 NOV. 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
