Popped Capacitors
xanadu
Posts: 3,347
Popped caps have been plaguing electronics for what, a decade now?
I've read a lot about popped caps and all the stories between stolen electrolytic formula to sabotage. I just want to know, when can we expect to stop seeing popped caps? If it were really a problem that existed so long ago, why are we still seeing new caps pop. The 'solid' aluminum electrolytic pop too!
I've taught a bunch of 'techs' how to replace them. Sometimes I don't think they should be replaced though. In some cases it seems like there might be some other problem causing the cap to go bad, and the new one might lead to frying something else.
So, what do you think? Is it just the electrolytic formula that 'goes bad' and in most cases replacing them will fix it? Or, is it possible that heat or current is the cause, and the poor innocent cap is the victim here?
In the 500+ motherboards I've repaired I've had a few come back popped all over again, so now I'm going to ask the pros here for advice. Thanks.
I've read a lot about popped caps and all the stories between stolen electrolytic formula to sabotage. I just want to know, when can we expect to stop seeing popped caps? If it were really a problem that existed so long ago, why are we still seeing new caps pop. The 'solid' aluminum electrolytic pop too!
I've taught a bunch of 'techs' how to replace them. Sometimes I don't think they should be replaced though. In some cases it seems like there might be some other problem causing the cap to go bad, and the new one might lead to frying something else.
So, what do you think? Is it just the electrolytic formula that 'goes bad' and in most cases replacing them will fix it? Or, is it possible that heat or current is the cause, and the poor innocent cap is the victim here?
In the 500+ motherboards I've repaired I've had a few come back popped all over again, so now I'm going to ask the pros here for advice. Thanks.
980 x 735 - 198K
Comments
High ambient temperatures or self heating caused by large current peaks at high frequencies are are a common cause of failure, particularly in switching power supply and PWM circuits.
Operating a capacitor close to its maximum voltage rating increases the risk of shorts due to wisker growth, and operating at higher temperatures makes the problem worse.
Ultimately the problem comes from using the lowest cost components that will do the job instead of one that has a bit of a safety margin in it's ratings but costs a little more.
http://www.antiqueradio.com/Dec04_Cantelon_capacitor.html
And that's just the start of the fun/danger. Some old TVs (and probably some radios) have a "hot" chassis. No isolation transformer from the AC line, in fact the chassis is directly connected to one side of the AC line.
http://www.techlore.com/article/16182/Getting-Started-to-Repair-Your-TV-Set----The-Ins-and-Outs/
The gutless, bloated, and fried power supply hall of shame http://www.badcaps.net/forum/showthread.php?t=8490
This is a very help full site when working on power supply or LCD monitor and LCD TV
I guess the problem is a combination of factors. I didn't know capacitors went bad, I mean did but not bad as in leaking. I have electronic equipment from the 80s and the caps are fine, however these devices are not on 24/7/365 and also don't use switching power supplies. It seems like linear power supplies may be less hard on the caps?
Anyway, I broke down and replaced the caps in the pictured power supply, all 1000uf 6.3v, replaced with 1000uf 12v with a higher tolerance low ESR rating. Not much choice in the matter waiting for another PSU even overnight wasn't an option. I did order one anyway as a spare.
I love the ATX spec, but these mini computers seriously need to start using ATX spec power supplies. It's complete BS manufacturers are allowed to produce 1000 different versions of one power supply that could be interchangeable. I'm writing a letter lol...
Initiation is done by charging one up, then tossing it to the newbie(while he's standing with his back to you) and shouting 'Catch!'...
Instant gratification of an exploding Cap is to put a Tantalum in backwards.
Jim
Good suggestion but you should also look for a better quality capacitor with a lower ESR rating as well. This is needed most for high peak current circuitry like switching supplies and PWM circuits.
As for capacitor lifetime being short, that is not necessarily true. A line of equipment made in the mid to late seventies came with electrolytic caps on the 5V supply (55,000uF, 16V) that rarely lasted more than a year. I replaced them with a 55,000uF 25V "CGS" (Computer Grade) capacitor and as far as I know none of the replacement capacitors died before the equipment was retired. I still get the odd service call on one that I installed in 1977. In most cases this equipment was left on 24/7.
I cannot comprehend how a manufacturer can choose the 'wrong' capacitor, after years of failures. That does not compute. Case not closed. When I find non 'low-ESR' caps in a device with a switching power supply I'm gonna go to work on the manufacturer with a screw driver and blow torch.
Higher voltage rating? = Costlier.
More Farads = Larger and costlier.
Lower ESR = Even more expensive.
Of course some companies will try to 'balance' the expected lifetime of the unit with the assumed lifetime of the components. They always expect a few to break before the sytem is obsoleted or out of warranty, but the cost of replacing those units can be much smaller than the cost of using good quality components throughout.
So in a sense it makes for 'good business' to use the cheapest stuff they can get away with.
If they calculate right, they save a bundle, with only a neglible loss of reputation.
If they miscalculate, or the components were a bit worse than anticipated...
(Anyone ever heard of an Bang & Olufsen system suffering from blown caps?)
Thank you Gadgetman. If that is true then I'm going to become a consumer advocate. Bang & Olufsen prices are a far stretch from a $0.03 cap vs a $1.30 cap. If I were to replace all the caps on a motherboard with low ESR it would raise the price by a couple of bucks, not hundreds or even thousands of dollars. I'm still not drawing the connection between saving money and producing a product guaranteed to fail.
Bang & Olufsen aren't expensive just because of good caps, but because they don't cut corners anywhere.
In my early days of field service contracts required regular Preventive Maintainance visits to clean filters and lubricate fans.
Once the cooling system was checked out the amount of AC ripple was recorded for all DC voltages and if it was too high the first thing to do was replace the caps. Most times that corrected the problem and saved having an emergency call out because a cap went pop.
One lesson that I learned is that electrolytic capacitors don't like to be hot.
It's funny because I remember always hearing to place the capacitors as close as possible but guess what happens when you stick them near a heat sink.
The electrolyte dries up, the capacitance changes, and pop goes the weasel.
Either the capacitors were underrated or the cheaper than dirt special of the week.
Hopefully your stash were from a reputable Japanese company.
I once had that happen to a Dell Optiplex design that I took in as partial payment for a job. The poor thing had its power supply in a really bad position. It managed to cause not one, but all of its power supply caps to explode.
I mentioned that carefully to the IT guy for the location regarding the whole line, it seems they were definitely aware of them, and did indeed get replacements.
Dell is blaming its own vendor for that problem.
Electrolytic caps do seem to fail a lot... I think Tantalum ones are better...
I think it's because electrolytic have liquid on the inside... Once it overheats, the liquid probably boils and pops the cap off...
Electrolytics boil, as discussed here.
Tantalums cause fires:
https://www.edn.com/electronics-blogs/tales-from-the-cube/4363362/What-a-cap-astrophe-
https://electronics.stackexchange.com/questions/99320/are-tantalum-capacitors-safe-for-use-in-new-designs
Ceramic caps can crack and cause dangerous short circuits:
https://www.edn.com/electronics-blogs/tales-from-the-cube/4406033/Stressed-out-over-capacitor-failure
At New York Toy Fair last February, I met Max Bogue, who invented the 3Doodler pen. He said a 3D printer failed the night before a big job was due, so they just broke the nozzle off and finished the print by hand. Necessity being the mother of invention, 3Doodler was born! That story roughly jibes with this article: https://www.forbes.com/sites/amyfeldman/2017/03/01/from-kickstarter-to-20m-in-revenue-how-3doodlers-inventors-built-a-business-in-3d-printing-pens
He tried selling it to the big toy companies, who all said no, so he Kickstarted it and laughed all the way to the bank. Never let someone else's lack of vision kill your dreams!
Unless it can make a profit quickly many companies will pass on it.
A-bad-capacitor-story-ends-happily
Funny you should mention Tracy because I notified the product engineer immediately when I found burnt caps in a customer return.
The engineer tells me that the customer caused it to fail and not to worry.
6 months later I see a few more returns with the same problem and then we are told about people commenting on tech forums.
Turns out the product works great except for with fluorescent lights.
Anyway we ended up having to make some hardware changes and rework thousands of units.
The capacitors weren't bad but the product was designed for ordinary light bulbs.
I threw the postcard away. By the time any damages trickle down to me from my minuscule purchases, I might have a check for ten cents to cash.
-Phil