Allen Bradley Plc

[alberto laville]

I have my power supply card that got blown last week,and i replaced it by a new .
To my expectations this afternoon i found that the new power supply
card is not working after it has been working for three days.
The plc is powered from a UPS.
Need help.
Alberto.

[just_lionel]

Sounds like it could be power spikes/brown outs and the UPS isn't doing its job. Could be a dead short, could be moisture (our problem at our plant, but it is wet all the time there)

[TimeFluxCap]

Sounds like a UPS fault to me. When was the last time maintenace was performed on the UPS?

[mgvol]

If it was a SLC/PLC-5 power supply, was the voltage jumper or selector switch set for the correct supply voltage?

[davidg68124]

Good Call mgvol. I was going to suggest looking at the same thing. By default, the ones I have gotten were setup for 220VAC

David

[Johnny T]

A long shot... but if you got the new PS card from your stores, it could be a bad batch of cards... I've seen this with a bad batch of inverters once whereby an inverter was dying at a rate of around one a week... Power supplies etc were investigated but it ended up being a bad batch of components in the inverters.

Could possibly be the same thing with your Power Supply although as I mentioned, its a long shot...

Is there any other equipment that is suffering or is it isolated to that one rack?

[Ron Beaufort]

I’d bet (pocket change only) that the UPS is the culprit ... but just for general ideas ...



have you checked to make sure that the power supply isn’t overloaded by too many modules, etc.? ...



are you using the 24VDC output screws on the front of the PLC power supply? ... if so, make sure that the load on that auxiliary circuit isn’t too high ... and also, check to make sure that the load on that circuit isn’t “spiking” back into the power supply ... think: inductive load being turned on and off ... compare with ignition coil on car engine ... 12VDC input from a car battery gives more than 20,000 volts output to fire the spark plugs ...



also check to make sure the chassis doesn’t have trash (metal filings, etc.) shorting out the backplane ...



and if you have another similar system on hand, there’s always the Fred Flintstone approach to troubleshooting a problem like this ... try swapping various parts (chassis, modules, etc.) from one system to another and see where the problem shows up next time ... (loud groan from audience) ... “swapping parts to troubleshoot?” ... yeah, I know it ain’t glamorous - but sometimes it’s the best way to nail a problem like this ...

PS Edit: whatEVER it turns out to be, PLEASE come back and tell us ... we all like to learn something new from time to time ...

[Rod]

I use component swapping. If you have a stereo amp and one channel is out then comparison is appropriate.

If you have two identical production machines and you swap parts you could put trash the machine that is in production.

That's diagnostics.

Rod (The CNC Dude)

[Jdesena]

Hello All,

I am new here. I am a student at a local junior college taking PLC classes. I just bought for my own learning a PLC 1760L12AWA from AB. I need the interface cable for programming. The cable cost anywhere from $68.00 to $75.00 US. Is there another way to get a generic or compatible cable for this unit? Where can I get the specs of this cable?

PLs help.

Thank you

Joe

[TConnolly]

I've seen something similar.

If its the same problem we had then it might not be the power supply. We had a rack go bad once. The power supply appeared to go dead so we swapped it out. With the new power supply installed, the PLC blinked on, then went dead. So we took the new power supply over to the bench and connected it to a test rack on the bench and it worked fine. Then we connected the old power supply to the test rack and it worked fine, so it wasn't the power supply. So we figured a card was pulling the system down so one by one we unplugged each module and turned it on. Nothing. The only thing left was the rack, and when we swapped it out, viola, it worked.