CompactLogix L18 losing program

This has happened several times over the last month. The L18, which is on a UPS, will lose its program and become unresponsive (all LEDs are off, too). A cycle of power to the unit will bring it back, and require a download. I have upgraded the firmware from v24 to v26 thinking this was the issue, but it has not helped.

I wanted to revive this since it's been over a year and more of these things are in production. While I'm sure it's a faulty unit, I was playing with it some more the other day. Sometimes it will run for 2 weeks, sometimes 24 hours, but will eventually shut off (no LED activity). Power cycling reveals a fault about Power Up Fault.

1769-L18ER-BB1B

My guess is its power sag related.
I have seen this when PLC power supplies fail (partially/not obvious)

Take the PLC off the UPS. Leave it that way for at least double the time between failures. See if the problem reoccurs.
Many UPS's are pieces of cr^p. I trust the less expensive ones about as far as I can throw one.

Sorry I should have updated this to say it is in no way related to the UPS. Subsequent testing was done on a regular outlet and several 24vdc power supplies.

Then the PLC power supply, serious ground leakage, or major RF interference.

GTUnit said:

Then the PLC power supply, serious ground leakage, or major RF interference.

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Definitely not RF interference either with plenty of other devices on same circuit functioning fine, including another L18.

Although if its power or ground issue, that's not an easy fix.

Can you run two units side-by-side and parallel the inputs?

Just thinking that if you can reproduce it on another unit, then the unit is not the problem and you need to look for something more weird. Ground loops on the IO do some weird sh*t with *SOME* IO cards that have ... interesting isolation ... from the backplane.

I have gotten rid of all of my CompactLogix (for durability reasons) and upgraded to full ControlLogix or downgraded to Micrologix 1100's or 1400's. The Full ControlLogix rack-based IO is harder for my electricians to break, but it takes more space and costs more. The Micrologix IO is different from the CompactLogix .. somehow ... and I have not had the same issues with the MicroLogix IO that I have had with CompactLogix. The electricians still break them, but they are less money to replace

I use 120 VAC inputs, relay outputs on the Micrologix. ControlLogix are IA16's on the inputs, OA16I's for motor and solenoids, and OF8's for interlocks to OEM skids.

Yes, I've ruled out all the obvious stuff. It is definitely unit related.

But thanks.

I would send the unit back to Rockwell and get them to fix it.

Is it worth your time? Unless this is a distracting mental exercise ...

I like how the people hired to fix things break the equipment.

The item is out of warranty at this point, and I'm sure the cost to fix it exceeds the cost to pick up another one on eBay. This is more or less for curiosity.

Do you lose the program every power cycle?

VAN said:

Do you lose the program every power cycle?

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If I cycle it while it's in running operation, no. But if it faults as described, then yes.

Not to rain on the parade, but why on Earth didn't you get it replaced under warranty ?

And if you're buying them on eBay in the first place, you shouldn't be surprised when you get sold a defective one by somebody who knew it would pass a quick test but fail a few days later.

Ken Roach said:

Not to rain on the parade, but why on Earth didn't you get it replaced under warranty ?

And if you're buying them on eBay in the first place, you shouldn't be surprised when you get sold a defective one by somebody who knew it would pass a quick test but fail a few days later.

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Picked it up fairly cheap for testing and I'm well aware of the risks of buying online. Just wanted to see if anyone had anything to offer other than the usual suspects. Apparently not.