AB SLC 5/03 going to fault after power failure

We have two setups with SLC 5/03 CPU. There was a power outage at our plant and one of the two went into fault after the power was restored. The program had to be redownloaded.

The second one was working fine. Initially, I though there was a problem with the battery of the first, so the battery was replaced but with the same results. Then the card was changed but with the same results. I changed the CPU even, but to no avail.

The fault occurs like this. When the power is restored, the fault light goes on but it is solid. When a second power cycle is given, it starts blinking and only then software can be redownlaoded into it.

So what could be wrong with it?

Thanks

Sounds like a power spike or something similar. I would consider some kind of power conditioning device to protect the rack power supply. Any communication cables connected to it? You may want to check that circuit also.

I ran into this once with it doing the exact same thing, first power cycle solid red light, second power cycle flashing red which you could redownload the program to.

Turned out to be a bad SLC power supply

In this case I would change the power supply of the plc rack. There was a post on this web site not that long ago try searching for it but it was a very simular problem to the one your having.

Grounding. It could be the power supply but first make sure your chassis is well grounded. We had the problem in our NJ plant with three different SLCs, every time the lights blinked they had to reload all three SLCs. I got brushed off when I told them to ground the chassis. Finally on one my my trips to that plant I personally grounded all the chassis. The problem never occurred again.

Thanks for the help guys. It was the power supply. I've replaced it and voila, it works fine now.

Now I've two faulty supplied with the same problem (work fine normally but the cpu doesnt retain the logic when given a power cycle). I was wondering what exactly gets wrong with the power supply to cause this behavoir? so maybe i can fix it or something.

Thanks

I know I'm a little late, just weighing in. I had the exact same problem 2 weeks ago. It ALSO turned out to be the power supply. The output measured 2 volts low... doesn't seem like much..... but it apparently it is.

A few years back I had a similar problem that turned out to be another card in the rack that was pulling the power supply down.

And yet another time it was a pair of slightly burned connectors between the rack and the power supply. Had to change both. I have quite a few of the SLC/503s in different customers' equipment. I carry a DTAM module around with me to make it easier to service them. They all have factory chips, so a reload is pretty simple if you have a DTAM.

:8I

Stationmaster

So anyone knows what actually goes wrong in the supply to make this condition?

Because other than retaining the memory, the supply works perfectly.

bump!!!

With out having the unit in our hands to carry out tests on we can only make guesses and my guess is that you have capacitors that are failing or faulty.

Identical Issue

I'm having the same issue with a new 503 it has OS302-Series C FRN 8 firmware. After cycling power (controlled) the CPU has a steady Fault LED and cannot be accessed. A second power cycle and the LED blinks, communication is restored but there is no user program, thus a download is required. The battery is new, and supplying a full 3v.

Does anyone know of any known anomalies with this particular FW revision? I'm relatively certain that this isn't a power problem, but I am wondering about the Chassis itself, as this machine has been out of service for 3 years and we only recently began the resurrection. When we first applied power the CPU was dead, so it was replaced with the new 503. On first power up Module 1 caused a CPU fault, turns out the module was bad, after replacement, Module 2 caused a CPU fault, it too was bad, then Module 3, then Module 4, then module 7 and finally module 8. So now I have all new IA16/OA16/OW8 modules in the chassis as well as the new CPU.

Everything now works properly, but the nuisance of having to download the program after cycling power is bugging me. Any suggestions would be appreciated.

Eric

I would pull all of the cards out of the rack and put a very simple program in the CPU to see if you can keep it running with just the rack alone. In fact, I would have done this test first before replacing cards, I've usually experienced rack failure before card failure.

Did you try changing the Power Supply only? In my case, replacing the supply fixed the issue.

I agree with sns...It is likely that a bad power supply was your root cause of all those other symptoms. I would replace the power supply and then recheck all those bad cards...if that doesn't help, replace the backplane.