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Testing a electrolytic Cap

Discussion in 'Troubleshooting and Repair' started by MichaelDP, Nov 18, 2014.

  1. MichaelDP

    MichaelDP

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    Nov 18, 2014
    I'm not a total noob to electronic repair, but kinda new to testing caps. I have a pc monitor that has know issues with caps on the power supply and I do see slight bulging but I just want to make sure and test it. I thought my multimeter could check caps.. But is it certain ones or itty bitty ones. The cap I want to test is 1000uf 16v 105c.. My meter has these settings
    20u, 2u, 200n, 20n, 2n. its a socket type so you just stick the cap into the 2 slots. But there is no ground side so maybe you cant check those types of caps with it. Is there another way to check them without having to buy another meter...

    thanks and new to forum Hello All..
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    You need an ESR meter to check the relevant characteristic of the capacitors, the actual capacitance is not particularly important compared to this.

    Buy same or higher voltage, 105C, same or slightly higher capacitance, and preferably low ESR capacitors -- and then replace them.
     
  3. chopnhack

    chopnhack

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    Apr 28, 2014
    Your meter won't be able to test that cap - further, the capacity testing of most meters isn't as reliable for many reasons. You would want an ESR of 1Ω or less to claim the cap as capable of continuing service. That being said, I too saved a monitor from an early demise by simply re-capping it. If they are bulged, its a good sign that they have to go.

    Damn, Steve - even with that finger you beat me to it! ;)
     
    Arouse1973 likes this.
  4. MichaelDP

    MichaelDP

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    Nov 18, 2014
    wow ty you both.. fast replies but more money for another meter.. lol.. thank you again
     
  5. chopnhack

    chopnhack

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    If you are an elec. enthusiast - you can go this route: http://ludens.cl/Electron/esr/esr.html or E-Bay has a bunch cheap if you can wait on them to come from China.
     
  6. MichaelDP

    MichaelDP

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    Nov 18, 2014
    ty again Chopnhack and Steve..
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Practically, even if you measure the ESR you'll probably change the cap out anyway.

    Show us a photo of the board and we can point out which ones are the likeliest ones that will need replacement.
     
  8. hevans1944

    hevans1944 Hop - AC8NS

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    Electrolytic capacitors are a real PITA. First of all: they AGE, whether in use of not. Second, they dry out as they age, increasing their ESR. Third, they fail catastrophically: leaking, bulging, sometimes even exploding. When in doubt, replace with factory new stock purchased from a reliable distibutor, not "new old stock" offered by an unknown e-Bay vendor. It is cheap insurance.
     
  9. chopnhack

    chopnhack

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    Apr 28, 2014
    Good points, but are there any alternatives? I have heard that tantalum caps can be quite dangerous as well.
     
  10. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Don't ever buy critical components on eBay - it's a counterfeiter's paradise. And for electrolytics, stick with reputable brands. The Japanese ones are best: Nichicon, Panasonic, Rubycon, United Chemi-Con (UCC). Other reputable brands (someone correct me if I'm wrong) are EPCOS, Vishay BC, Kemet, Cornell Dubilier (expensive), and maybe Elna.
     
    hevans1944 likes this.
  11. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Hi John
    TANTs are not an alternative for Electrolytics they have different characteristics which may not be suited as an alternative. For some applications it's desirable to use a TANT over an electrolytic if leakage current is a problem.

    I stopped using TANTs in my design a few years ago because of the fact they are expensive and I don't agree with the disruption of the Gorillas in the CONGO.
    Adam
     
    chopnhack likes this.
  12. chopnhack

    chopnhack

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    Apr 28, 2014
    Hey Adam :)

    I took a look around and it seems film capacitors are the closest alternative to electrolytic caps. There are limitations though - seems as you get above 700μF or so they don't make film caps (at least I didn't see any in a quick search). This was a good link discussing the limitations of electrolytic caps and some workarounds:
    http://www.eetimes.com/author.asp?doc_id=1279791
     
    Arouse1973 likes this.
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