Somebody had mentioned bad capacitors in a MicroLogix

[Skidood]

I'm hoping I can get a little more info on this. My 1400 made a loud snap sound the other day after powering it up. But it seems to be working just fine.
What part of the PLC circuitry are these problem capacitors in? How hard is it to open this PLC up and go looking for a blown cap?

 

[TheWaterboy]

A loud snap? that should be easy enough to locate.
Give it a go. Electrolytic caps dry up over time. Just replace them all.

 

[Skidood]

In college, we would wire an electrolytic cap across a 120 VAC power cord and marvel at how loud the bang was...I'm sure we weren't the only kids who did this...

 

[jraef]

How old is it?
Was it sitting on a shelf unpowered for years?

 

[Skidood]

Built in March 2012
Don't know how long it was sitting, I bought it on eBay. It doesn't look like it has been used much. Why do you ask?

 

[jraef]

Electrolytic capacitors that sit on a shelf with no power on them for years will degrade and when you power them up, they are a dead short inside so they pop. You have to go through a careful process of slowly increasing the voltage over the course of hours so that they can “reform” the oxide layers on the films inside. It’s one of the risks of buying electronics used from Fleabay and places like that.

As mentioned you might get lucky and the cap acted like a fuse, saving other components on that circuit. You will have to open the case, look for the popped cap and replace it. I would just replace them all if going to that trouble.

 

[Aabeck]

I had a control off a stamping press clutch 'repaired' by a local repair shop, then it turned out it wasn't the control card at all but this clutch had DC brushes.

I had to press the repair shop to exactly what they found wrong to charge $185 for the repair, and after a lot of questioning they admitted that as soon as they get a repair item in they replace all the capacitors, then test it. It tested OK so they figured it was a capacitor.

I still have a problem with $185 to replace about $6 worth of capacitors that were on the card, but since then I check capacitors first when something isn't working - unless there is an obvious blown component.

 

[mikas_m]

Electrolytic capacitors that sit on a shelf with no power on them for years will degrade and when you power them up, they are a dead short inside so they pop. You have to go through a careful process of slowly increasing the voltage over the course of hours so that they can “reform” the oxide layers on the films inside. It’s one of the risks of buying electronics used from Fleabay and places like that.

As mentioned you might get lucky and the cap acted like a fuse, saving other components on that circuit. You will have to open the case, look for the popped cap and replace it. I would just replace them all if going to that trouble.

Is this also the case for PC motherboards? For one industrial PC, I have ordered a spare motherboard. It was on a shelf for about 8 years, and when needed. First time it was powered it didn' t work well. The system hanged during BIOS phase. I blamed a company that delivered motherboard, but there was no warranty after that long time.

Where can I learn more about this?

Thank you.

 

[mister x]

Additionally, just because it snaps, that doesn't mean you'll see the problem. I had an AB CGCM pretty much tear my head off with no signs of damage. Started right back up lol.

 

[jraef]

Is this also the case for PC motherboards? For one industrial PC, I have ordered a spare motherboard. It was on a shelf for about 8 years, and when needed. First time it was powered it didn' t work well. The system hanged during BIOS phase. I blamed a company that delivered motherboard, but there was no warranty after that long time.

Where can I learn more about this?

Thank you.

8 years (plus how ever long ago that happened) might have put it into the time frame for the infamous "capacitor plague" that took place from around 1999 to 2003, but had ripple effects into 2007 for some manufacturers, especially PC mother board mfrs. That little episode cost Dell around $3 billion!