CPU Fault on power loss on a slc 501

[rrparker07]

Thanks for the info Ken. I now know not to try that again. I apparently got lucky this one time because its functioning fine once I reload the program. It has also accepted a new program with only two rungs I ran as a test to see if the fault still happened.......it did.

 

[rrparker07]

don’t just go pulling the processor while you have the power on especially if you know that this isn’t a "preferred method"

While I appreciate the fact you're trying to help me, Ken and yourself have already told me that wasn't a good idea.

Let's keep the piling on to a minimum

 

[Ken Roach]

It's been a long while since I worked on a 5/01 controller; the operating system of the 5/01 goes back to the late 1980's and it was almost completely replaced by the 5/03 as soon as that came out in 1993. If I was going to replace the controller I'd use the 8K version of the 5/03 rather than trying to get an actual 5/01.

The key symptom that I see is that the controller seems to be reporting that the user program has been erased; you mentioned that it reports the online program name to be "no program".

So, this isn't a conventional fault. It's not a misconfigured I/O slot, or a divide-by-zero, or something else related to the user program. It's a failure that happens when the operating system first boots up on power-up.

If you happen to have an OPC-capable version of RSLinx you can link the S:6 status word to Excel or the OPC Test Client or the Data Table Monitor to check if there's a useful value in there.

I've seen power-cycle problems related to the power supply (sometimes it's the 115/230V switch) and the chassis and the CPU. Which one you change out depends on what you've got for spares and testing. If it were me, I've got a bunch of spare 1747 chassis and power suppplies that are known to be good so I'd put the controller into one of those to test it.

 

[rrparker07]

Thanks to all that helped me out.

The power supply was the problem. I incorrectly ruled that out when the processor still faulted when pulling and replacing it under power (which I will never do again). I sometimes let my eagerness to solve a problem get in the way of my common sense.

Thanks again,
Roy