PLC5/80C: Lost its program

[Conor 4]

Hi guys, I was wondering if anyone might have any idea's on this. I was called in yesterday evening for a PLC problem. I found that one of my main PLC's has "Lost" its program. I was able to download the program to the PLC, and got everything back up and running ok. I was wondering how the program was wiped? The only way that I can think is that there was a power outage and that the battery was dead. This PLC is backed up by a UPS. There are two redundant in-rack power supplies. Not sure when the battery was changed last, but think it was about 3 years ago. I have looked into the power outage, and can't seem to find any issues around the rest of the plant where the power dropped, so I don't think that this was the problem. I am a bit baffledand also worried that this could have happened. I was online to the PLC yesterday and had saved the program before leaving work at the normal time. If anyone has any idea's/thoughts/suggestions I would be very gratfeul. Thank, Conor

[Mickey 71]

Other then power issues check grounding. Also make sure you have surge protection on all inductive loads.

[Joe E. 259]

I know this is an old topic, but also make sure all of the modules are fully and firmly seated in the chassis and that whatever locking means your chassis has is applied. We have in service some with the hinged metal bar and others with the plastic latches. If one is left unlatched, it can vibrate loose and cause weird things to happen, up to and including the processor wiping itself.