Slc500 Fault Information

I'll try to be brief, long story short I'm tasked with bringing a packaging machine back from the dead that has a re-engineered control system installed by our long gone PLC whiz kid.
The machine sat with no power source for months and had no battery back up. When we powered it up I got the dreaded CPU Fault flashing light.
The device is a 1747-L240A Processor 12 115 VAC 8 RLY Out with one 1746-IA 16 16 120vac inputs and one 1746-OW16 240vac Relay outputs.
Figuring I already had lost the program I found an old hard copy of the program and rewrote it so I could load it back in to the processor, but I keep getting a Fault immediately when I try to put it in the run or test mode.
The fault (56h) says the rack configuration specified in the user program is being detected as incorrect.
I have went back through all the configuration parameters and as far as I can tell everything is as if should be.
The fault clears, but comes right back when I try run or test.
Could I have a bad input or output board that the processor isn't recognizing?
At one point I was getting a different fault saying run time error something stuck in the out put card, now that has gone away and I keep getting the rack configuration fault.
Anyone out dealt with this before?
I'm pretty sure the configuration is right.I don't have another input or output board to try at this point, but that would be my next move.

1747-L240A

Click to expand...

I don't have one of those listed in my RSLogix500 software ... please double-check the number ...

can you post your .RSS program file? ... you'll have to zip it first - forum rule ... maybe we can help you spot something there ...

Sorry my screw up the processor is 1747-L20A I can post the file but it'll take a little doing I'm working with an old computer with Windows 95 and it's not online. I'll have to print a hard copy, scan, etc. But it can be done if needed.As I said I copied the program from the original and it worked great for years, I have some PLC programming experience but not on this old stuff. I had to learn the Allen Bradley just for this.

scanning and posting a hard copy probably wouldn't help us much ...

can you just copy the RSS program file onto a disk (etc.) and then move that over to an "online" computer? ...

I'll see what I can come up with, everything's at my workplace so it'll be tomorrow at the soonest, I'll try to get something out to you in the next couple of days.
Thanks for the help!

according to what you've posted, your I/O should look like the figure below ...

does it? ...

and incidentally, a "stuck runtime error" is often the result of placing a module into a system while the system is powered up ... it also can occur if the module's connection to the chassis is intermittently faulty ... you might want to check the connections - and maybe use a good quality contact cleaner if the connections look cruddy ...

.

If your I/O Configuration all checks out...

Your 2-slot rack might be defective...

17886 - Defective SLC I/O Rack Error Codes
Access Level: TechConnect

Regards,
George

Yes that's exactly what it looks like.

I do know enough to not put in or take out boards while powered up, so I know that didn't happen from me, intermittent connection is always possible I guess. As I said the stuck run time error was what I was getting at first, since then I have had the I/O modules in and out a couple of times, and I don't seem to be getting it anymore, just the rack configuration fault.
If my configuration is correct, and I believe it is, what else would give me this fault? I guess that's the $64 question.

Have you read my first post, maybe you missed it?

Did you (can you) read the link?

Regards,
George

I've just realized that no one can read that link! I must have made an error while copying the URL?

Here it is again...

17886 - Defective SLC I/O Rack Error Codes
Access Level: TechConnect

Regards,
George

If your program is gone clear the processor memory then start a new project and use Read I/O config to read the I/O configuration to confirm that your processor is recognizing your modules.

Sorry my screw up the processor is 1747-L20A

Click to expand...

Could the processor have been swapped out at some time, and the one in the rack now really is a -L20R, or -L30A, or -L40A?

RoddyBiff; said:

Could I have a bad input or output board that the processor isn't recognizing?
At one point I was getting a different fault saying run time error something stuck in the output card, now that has gone away and I keep getting the rack configuration fault.
Anyone out dealt with this before?

Click to expand...

Yes and Yes to both questions.

Uhh, I would yank the output card wiring arm and try again. I have seen this fault caused by current spikes in 1746-OW16 relay cards several times. If you can go green with no load great, but if not, try a new card. You particular description of symptoms sounds more like a fried card to me than a load issue or backplane problem. Don't be surprised if you find that your input card is the culprit and the SLC is lying to you about the slot number. Not the the SLC would intentionally try to deceive you, but it is often just confused by the **** coming back across that bus.

I once spent two weeks hunting down a 1746-OW16 noise problem I nicknamed the "blame your little brother fault" because for the first six or so occurrences, the fault was pointing at the slot to the left of the one driving the "noisy" hydraulic solenoid. During the problem I was chaisng the machine would run for a few hours sometimes and some of the faults were the "rack stuck fault" and card faults "slot unknown" sometimes but mostly the problem child in slot 4, if I recall, was blaming it all on slot 3 even after I moved a card from slot three to spare slot 2 and slot 3 was empty!

Okie, love the pup by the way, Thanks to you and all the other folks out there that helped me with this, I finally got it sorted out today. As best as I can tell it was a connection error between the processor and the rack connector. I took the whole thing out today and reseated all the connectors and when I re-installed it the faults went away.
Now I'm just debugging the program, hopefully I can work my way through that, I'm a little shy of expertise in Sequencer logic, but at least I have fighting chance now. Once again thanks to all.
Till next time?!