SC 553 on a RC4500

[rednecktech]

Hey guys,

We are getting a SC 553 on a C4500. We have swapped fusers and tried a new IOB. The service manual points at the BCU or the PSU. Before we order anymore boards, I was going to see if anyone else has seen this and what they did to fix it.

What originally happened was, I went to help a techncian on this machine. He put a new fuser in (811 fuser) for a SC 548 if memory serves me correctly. He swapped the harness with the two thermistor wires (the only difference between the 811 and C3500/4500 fusers. Could have just moved the blue wire from slot 1 to slot 2 and unplugged the little white connector instead). But, when I got there he had started getting the SC553 and couldn't clear it. When I pulled the fuser out I noticed the white connector plugged into one of the thermistors was hanging over onto the fusing belt. It had melted and I could see the wires exposed across the connector. At that point I knew that something got zapped, probably the power supply.

I wanted some other opinions before we start throwing more money at boards. Thanks all!!

[Fearless V K]

Repair the faulty connector wires, replace the thermopile (can cause the 553), and check the IH inverter coil fan, the blades can spin on the shaft and cause the 553 also. (the fan motor is still spinning, so you don't get a fan code).

[rednecktech]

Thanks Fearless, By thermopile, you mean thermostats/thermistors, correct? There is a brand new fuser in it now so it should eliminate that being the problem.

Is the IH converter fan to the right of the fusing unit. If so, this one is definitely working. As far as it spinning on the shaft, we will check that.

[teebee1234]

Last time I had this error (over a year ago) on this model, it was the PSU.

[Jomama46]

Thanks Fearless, By thermopile, you mean thermostats/thermistors, correct? There is a brand new fuser in it now so it should eliminate that being the problem.

Is the IH converter fan to the right of the fusing unit. If so, this one is definitely working. As far as it spinning on the shaft, we will check that.

No, he means the thermopile, it is not part of the fuser, it sits in front of the fuser, see parts cat pg113 #11

But my money is on the PSU

[Fearless V K]

the IH coil fan is on the LEFT side of the fuser. you need to take off the covers there to see it. never had to replace a PSU on these before but it should be easy enough to check power output if you suspect that.

[Venom]

I think it is the thermostat that is left in the copier at the bend where the fuser belt almost contacts when fuser is installed. The little black square of the thermostat can be popped out with a pin or knife. Underneath the black square is a button that gets held in when black square is popped. The SC code will automatically reset, 5810 isn't required to reset it.

[rednecktech]

Ok, this what we have tried.......We put a new BCU in and the copier came to ready and made a print. We put the covers back on only to have it code out (553) again. Next we tried a new power supply with no luck.

We are getting overheat on the end thermistor, center one seems fine.

This leads me to question the thermopile. Without getting into the service manual, what is the function of the thermopile?

Thanks again for the replies, I will post the outcome.

[TonerMunkeh]

The thermopile is another line of defence in overheating. It sits in the middle of the IH coil.

[rednecktech]

Thanks TonerMunkeh, I have located the thermopile. Do you think it could have gotten shorted out when the thermistor was damaged originally? This all started after the outside thermistor"s connector was melted to the belt. How he even managed to get the cover back on with the thermistor wire being out of the "slot", I dont know.

Is there any way to check this thermopile with a meter?

Thanks again........the saga continues.

[TonerMunkeh]

I'd say it's a fair bet it's blown. I don't know if you can check for continuity as I think it works more like a thermistor than a thermostat.

Either way, I'd change it. If it still gives you 553 after that, I'm willing to be the IH coil or IH coil PCB has been blown. If so, replace the coil, PSU and thermopile as a set. Keep the old main PSU handy as well, you might be needing it.

Failing that, you'll have to strip the living piss out of the machine and check the harnesses for heat breaks.

[rednecktech]

Update: We pulled the thermopile for a visual inspection, put it back in the machine and now we're getting a SC120 followed by the 553. We can move the scanner across to see if it goes back to home position which it does not. No lamp turning on or anything. We go to do input check on the scanner section and the screen freezes up. Why would pulling the thermopile start causing a scanner home position code?

We are going to order the thermopile, IH coil and IH coil pcb. Should we put the old psu in at this time?

[TonerMunkeh]

What a nightmare this machine is turning out to be! If you've already replaced the BICU I think the IOB might be the next step, especially if the machine is mis-detecting sensor readings. If you can, order the IOB and the parts mentioned above and fit them as a set.

[rednecktech]

What a nightmare this machine is turning out to be! If you've already replaced the BICU I think the IOB might be the next step, especially if the machine is mis-detecting sensor readings. If you can, order the IOB and the parts mentioned above and fit them as a set.

OK, we have solved the 553 and are able to make internal prints. I replaced the thermopile and the IH Coil pcb and it didn't lthrow the code after this.

BUT... the 120 is still there. I tried a new scanner board, the scanner power board and stepper motor. The 120 didn't come until after we took the original thermopile out to take a look and put it back in. Weird.........So YES, this machine has become a bit of a nightmare and the customer wants it back!!

[teebee1234]

Maybe during the process of removing and replacing the thermopile some other harness got pinched/pulled. Did you have to remove any other connectors to remove the thermopile? If so, a bent pin could have occured when reseating one of them. If no good, the next step is to us an M80 to blow everything back into place.