SLC 5/05 Faulted

Here is the thing...

A customer reported several times PLC module faulted without any reason after 8 years of continuos working, according to maintenance crew it comes to RUN by itself after several hours powered off and the power up.
The last fault happened during a lightning storm, power went off for like 5 minutes and then came back, but the FLT was on and all the other LED's where blinking. I wasn't able to connect using ethernet cable I changed to use the CP3 cable and was able to connect to the PLC and it came to me the error 0001 (NVRAM). I downloaded again the program, change to RUN, program up and running again, power went off again and came back but now I wasn't able to connect to PLC even with the CP3 cable. So we turn off the CPU during night and power up again in the morning and the program was there and PLC at RUN state.
Does any one have a clue about what is going on with the CPU?

Do you have a spare you can set up and load, stick a battery in it and just swap processors? I would get a spare CPU module ready. SLCs are pretty good at reporting the source problem...Can you upload, save, zip, and attach a copy of the file to this thread? If it is configured for an EEPROM, ensure that you have laid eyes on it during the next failure. Check the backplane connections, and grounding conductors, and a spare cards ready.

Power supplies can affect SLC memory integrity, but usually, they will only "wipe themselves" and appear as DEFAULT processor name, refuse the upload option, etc...

Yes, power supply is the cheapest and about as quick to exchange, but you need spares for each...chek the power supply voltage for ac ripple, and look for swollen capacitors when you have it out. Make sure the battery is fresh and all the terminals clean, and nothing looks damaged, and ensure a well mounted backplane (I onced replaced a 13 slot chassis because a guy left out a screw, and later on loose wire trimmings and a washer slid behind the backplane like a wedge. The later told me that machine had "card eating binges for years until I had to remount it in fresh tapped holes...).

I have had SLCs do all manner of failure, I know that if the Fault LED is doing ANYTHING, I get my spare ready...I had one that would put itself in remote program spontaneously with nothing connect to any of it's ports! I have seen dozens of them wipe them selves due to a bad smart card putting trash on the backplane. Logging the actual Error codes status words from an HMI is very useful in this case...

Often, the "DEFAULTED" SLC will reset its channel 0 properties to factory default. Last weekend, I had a 5/03 connected DF1 @ 19.2k "wipe itself" to prevent unwanted actions, and set the baud rate back to 1200!

I don't recall all the default data rates, but that can prevent an HMI from accessing those values for logging.

If it successfully loads and runs after a long power outage, I suspect a possible battery problem along with an existing SLC Memory Module being loaded after a lengthy power outage. I don't recall ever having the CPU report battery status through it's LED incorrectly either.

I have fixed* more than I can count on one hand with a big fat green AWG 10 wire and nice unadulterated ring terminals properly connecting the first bottom chassis mounting screw to the system ground.

*by "fixed" I mean I made them more lightning and electrical fault tolerant by following the grounding guidelines for the power supply and chassis from the SLC Modular Hardware Style user manual.

SLC's seem to have a big problem NVRAM error (this seems to happen when powered down or up). the last one I had I stuck an Eprom in & never had the problem again but good earthing, and a mains filter should help.

Thank you guys for your answers... The file is attached to the post.

I already check power supply and it's ok. Maybe I think the grounding it is the problem.

About the EEPROM, the CPU has one but seems to be corrupted, I don't know really, for me SLC are a little bit old for my knowledge (I am a little bit rookie with 'old' PLCs).

So yes, customer already ask to supplier for a new CPU + EEPROM so I will also recommend for a better grounding system including the 10 AWG cable to the chassis.

I can repair or purchase your nonworking unit for you if your interested.

[email protected]

Marc02x4 said:

Here is the thing...

A customer reported several times PLC module faulted without any reason after 8 years of continuos working, according to maintenance crew it comes to RUN by itself after several hours powered off and the power up.
The last fault happened during a lightning storm, power went off for like 5 minutes and then came back, but the FLT was on and all the other LED's where blinking. I wasn't able to connect using ethernet cable I changed to use the CP3 cable and was able to connect to the PLC and it came to me the error 0001 (NVRAM). I downloaded again the program, change to RUN, program up and running again, power went off again and came back but now I wasn't able to connect to PLC even with the CP3 cable. So we turn off the CPU during night and power up again in the morning and the program was there and PLC at RUN state.
Does any one have a clue about what is going on with the CPU?

Click to expand...

I've ran into this before, twice actually. While I could find no physical evidence swapping the chassis solved the problem. Also, in both situations proper clearance guidelines above and below the chassis had not been adhered to so I suspect long term overheating was the culprit.
http://forums.mrplc.com/index.php?showtopic=13336