SLC 5/05 "Internal software error" ?

Hello,
I have been experiencing a SLC 5/05 fault which has been occurring at what seem to be random times. It has happened about 4 times in the last 2 weeks. To get the PLC running again, I have been re-downloading the program. Even though this "fixes" the problem, I have no clue why, and what's causing it, and how I can really fix it so it will not happen again. Here's some additional info that might be helpful, along with a pic of the screen I got this morning when I went online with the faulted plc and clicked "go to error". Also BTW, I'm new to PLC's, and this is my first post, so please bear with me. Thank You, Byron

- the red battery LED indicator is on steady which means I guess the battery needs changing?
- when this happened the other times, I couldn't even go online or upload. Performing a download was indicated by a dialogue box to be the only option. And i believe I recall seeing "no user program" at one time.
-When trying to get online with the faulted PLC...the RsLinx window would show the plc with a red X on it, until I cycled the power on the plc, then Linx seemed to see it again.
- This does not seem to be associated with any power outages or brown outs.
- Clicking "clear Fault" or "clear major error" does not work.
- The original programmer/provider went online with the processor the first time this occurred and indicated he found (and fixed)an issue with the RTC in the status files. I didn't see what he did though. He is not a readily available resource, so I'm not getting a lot of info from him.

Thanks again for any help you can provide!
Byron

See picture below for more info on error code "8h"

And post your program if you can zip it first.

Thank You Mickey,
I will have to see if i'm allowed to post the .RSS, I may have problems with that. Of the possible causes, can I possibly eliminate some based on the fact that this is a newly occurring issue, and this system has been fairly trouble free for a couple of years or more?

Is there a recommended method for verifying that i don't have a "poor power source"?

I have a standard multimeter but that's about it.

Regarding the possibility of "noise". The PLC panel is located faily close to 3 pump motors, running on VFD's, and motors have shaft grounding devices installed (shaft grounded to stator). If the shaft grounding brushes have worn out, could we have increased ambient "noise" from that situation? I'll go check them.

The PLC ground goes to a common earth ground rod, solid copper, nearby, outside, maybe 20ft away or less. I will go check the lug connections.

Thanks again,
Byron

Make sure the PLC chassis is bonded to the ground with a copper ground lead, not just relying on the backpan ground and/or the power supply ground. You can bond the chassis at any of the chassis mounting tabs. Rockwell recommends chassis bonding and I've personally seen a case where mysterious program memory problems disappeared as soon as the chassis was bonded.

Is there a recommended method for verifying that i don't have a "poor power source"?

Click to expand...

You may need specialized equipment for this one.

Don't discount surge protection on inductive loads.

Thanks for the replies,

One question about surge suppression on the inductive loads: I have been assuming that isolation relays provide sufficient suppression. We use the slimline AB ones. I think they may even have a built in diode for surge suppression too, but not sure. Should there be additional protection?

So I went to the field and did some more investigating. What I eventually found was this: the neutral/L2 from the powerline filter that feeds the PLC AC power input was totally loose. In fact im not sure how there was even a circuit being made at all. When I powered down, the wire just fell right out when I just barely touched it.

So do you guys think this was likely, or possibly my issue?

Thanks,
Byron

It might be. Correct it and see if the problem goes away.

Its possible that you have had the problem for a while but your battery masked it, until it went dead. Depending on the process and the PLC program I suppose its possible that the PLC might momentarily loose power and you might not notice, or you might have noticed some quirks that you couldn't assign a cause too. Once the battery was dead and you started loosing the program then it became more obvious. Just a wild guess. At any rate, while you are at it make sure you replace that battery.

BTW: Do replace the battery.

Wasn't the loose wire - Faulted Again this morning

The loose wire was no to blame. I corrected that yesterday, and the PLC faulted again this morning. I will be picking up a replacement battery this afternoon to install tomorrow morning. Based on the dialoge box shown, this seems to be a possible cause for this issue. Have you guys seen this happen before due a to dead battery? I would not think this would come into play unless there was a power interruption? Any ideas?

Thanks for all the help, this place is great!
Byron

The SLC platform CPUs are notorious for being extremely finicky when it comes to supply power.
Just make sure you are using a top tier power supply, monitor its functionality, install fresh batteries at scheduled intervals and, if possible, do not use the same control power "provider" device for both the controller and the I/O; I have experienced quite a few CPU hard faults due to defective I/O circuitry/devices.

even if you replace the battery, i strongly recommend a surge suppressor. we use the corcom brand.

i had a 5/04 that lost its program and it was due to power spikes and dips.

when we added the suppressor, the problem went away and we standardized on them. haven't had a problem in over 20 years.

regards,
james

Thank you Dmargineau and James,
I will need to check to see if the controller power has it's own dedicated circuit. It has functioned well for at least a couple of years, and no new I/O or wiring have been added.

James, the PLC power is fed through a cutler hammer surge filter. However i'm wondering what these devices can do for a low power condition,...as in maybe we are getting drops/undervoltages, not spikes that could be causing issues. I'm going to look into how the power is distributed across our site, as there was some HVAC equipment commissioned recently. That equipment is located in a different building, and no problems have occurred with the process equipment there. (there's a micrologix 1100 running in there too)
Thanks again,
Byron

You may be having a problem with the PLC power supply. Racks have been known to go bad as well. You should be fine without the battery unless the power supply to the processor is interrupted.

Go ahead and replace the battery but if the problem goes away when you replace the battery then keep looking for the root cause.

I suggest you add a rung XIC S:1/15 CTU C5:?? 0 0. Look at the value of the counter ACC in a couple of days. It shouldn't show any more first scans that what you can account for. If it does then you've got a power supply problem.

Update - and Question re AB hardware purchase

Luckily a local friend was able to loan me a spare 5/05 he had on hand. I put it in, and so far, we've gone 7 days without any faults or issues. So it looks like I'll need to purchase a new one.

Here's my question:
There seems to be some "deals" available on the internet and elswhere, on "new in box" allen bradley PLC's and modules. Are there some compelling reasons why I need to buy from Allen Bradley?

Thanks,
Byron

If anyone needs any slc 505 repairs ind-concepts.com is the cheapest and fastest turnaround place to go.