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Super Hot Capacitors...!

Discussion in 'General Electronics Discussion' started by Mark69, Dec 13, 2016.

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  1. Mark69


    Dec 13, 2016
    Hi Guys,

    I wanted to get some advice about capacitors in a power supply which are getting super hot....!

    I bought myself a secondhand Xbox One console which turns out the PSU is not the original Microsoft one but a Chinese aftermarket product.
    It works but the case gets very hot on the top, on the bottom there are two large areas of the case with slight visual disfigurement, there is a slight melty plastic smell after 20 minutes of use and the fan noise varies from whisper quiet to squeaky at times.

    I opened up the PSU and inside it looks like it is constructed to a budget with a cheap fan without any airflow guide.
    The 3 main capacitors seem to be;
    1 x 150uf 400v 85degree on the AC side - looks absolutely fine
    2 x 2200uf 25v 85degree on the DC side - one is bulging and both have singe marks around the base on the PCB

    So, I put the PSU back together and played the console for an hour - the PSU was hot on the outside with plasticky burning smell. I took it apart to measure the temperature of the capacitors with my infrared thermometer;

    On the AC side the large capacitor is touch warm at 40-45 degrees C.
    On the DC side the 2 capacitors are showing as 120-130 degrees C - you can feel they are super hot just by hovering a finger above them.

    So my question is what would cause this capacitor situation in my PSU? (crap caps/inadequate cooling/something else)
    Should they have failed by now? (85 degree caps regularly heating up to 130)

    Should I try a quick fix and replace them with uprated ones - 2200uf 50v 105degree ones?


  2. Alec_t


    Jul 7, 2015
    Sounds like the hot caps have too high an ESR. Replace them with good quality low ESR 105C types.
  3. Chemelec


    Jul 12, 2016
    That Capacitor that is BULGING, It is BAD and Needs Replacing.
    Capacitors should NOT Heat up if they are good.

    The Temperature rating on the Capacitor is for a Maximum Air Temperature around the Capacitor.
  4. IamJatinah


    Oct 28, 2014
    Correct. Bulging capacitors are a sign of outgassing, the final stages of a capacitors demise. All capacitors listed should be replaced, as well as one you may not have mentioned, that should be somewhat near the 150uf cap, that lives in the primary power circuits, maybe 100uf or 47uf, but this should also be replaced. There are more than 3 caps in that power supply, and all caps in there have been exposed to high temps ;o)
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