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Exploding 600w ATX PSU!

Discussion in 'Electrics UK' started by eveares, 8 May 2015.

  1. eveares

    eveares

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    Ever tried powering up a 8 year old computer PSU by shorting pin 16 (PS_ON) and 17 (COM) together on the main ATX power connector.

    Well I did, and it powered up and ran fine for about 10 seconds before making a loud pop and whoosh sound whilst releasing lots of obnoxious white smoke and leaking horrible brown fluid! (side note: What is the brown fluid and will it wash out from my bed cover?)

    Lets just say one of the main Caps inside failed catastrophically!


    Glad nothing was connected to it!

    EDIT: http://www.urbandictionary.com/define.php?term=Fuhjyyu :rolleyes:
     
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  3. PrenticeBoyofDerry

    PrenticeBoyofDerry

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    Is this from the PC or another accident you had :?: ;)
     
  4. JohnW2

    JohnW2

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    Frequently! Anyway, let's face it, that's exactly how the 'on' button of a PC does it.
    Obviously a risk with anything containing large electrolytic capacitors, particularly if old, and even more particularly if not powered up for a long time. However, if that were destined to happen, it would obviously happen when the PSU was powered up, regardless of how one achieved that.

    Kind Regards, John
     
  5. bernardgreen

    bernardgreen

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    When resurrecting an old power supply or anything else with electrolytic capacitor the risk of a capacitor "boiling out" is significant.

    If it is essential to use the item then the risk of a boil out can be reduced by re-forming the capacitors by applying a very low DC voltage to them ( via a resistor to limit the current in case the capacitor is beyond repair. ) If the current drops after time to be close to zero then slowly increase the voltage.

    The majority of electrolytic capacitor are constructed from two long strips of aluminium foil ( plates ) separated by paper soaked in solution of a chemical that is conductive. These are then rolled up and put into a can or other package, As such they are NOT yet a capacitor. They are then "formed" into a capacitor by applying a voltage to them. The current causes the chemical to react with one of the plates to create a thin layer of oxide ( or other compound ) This layer is an insulator and thus the capacitor is created.

    Over time if the capacitor has no voltage applied the oxide layer dissolves and then when voltage is applied the capacitor current will flow from plate to plate through the liquid. This heats the liquid up to and beyond boiling point. The oxide starts to form but is detached from the foil by the high current, hence the current limiting resistor when forming the capacitor.
     
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  6. eveares

    eveares

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    No no no other accident, It's from when the cap in the PSU catastrophically failed, sparing out brown liquid and releasing tons of smoke. The old and unused PSU was on my bed when it failed.
     
  7. Adam_151

    Adam_151

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    Just sleep on the workbench instead....
     
  8. bernardgreen

    bernardgreen

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    Give some thought to locations for testing and sleeping.

    Two rules apply

    Failures are allowed, even expected, on the work bench.

    Failures are not expected in the bed and if they happen the results can be catastrophic.
     
  9. eveares

    eveares

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    Luckily my bed did not go up in flames :rolleyes: ;)

    I blame the cheap and C**P caps inside the PSU!
     
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  11. JohnW2

    JohnW2

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    Well, it was 8 years old! had it been unused for a long time when this incident occurred? As for cheap capacitors, when you see how cheap OEM ATX PSUs can be, it's hardly surprising that they use cheap components!

    Kind Regards, John
     
  12. RI1982

    RI1982

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    What make was this PSU? I suspect it was a cheap Chinese brand and probably can't even handle 300w yet alone 600w.

    I actually want cheap power supplies to be banned, there are too many dangerous ones getting into the country. I am not just talking about ATX power supplies, iphone chargers etc.

    It seems some suppliers think just because it says CE on them they are safe and meat the relevant standards.

    Personally when it comes to ATX power supplies I always over spec them and buy proper brands like Corsair etc. I realise Corsair don't make the PSUs but they do at least carry out testing and make sure it is made to a half decent standard.
     
  13. SimonH2

    SimonH2

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    Consider yourself lucky that the can is deliberately weakened on modern caps. I recall years ago someone telling me about reforming caps (in the context of powering up old (valve) TVs and radios), using a variac to slowly wind up the voltage. Go back a while and caps tended to have stronger cans and a hard seal - thus internal pressure could build up considerably before anything lets go.

    He told me on one he'd had where the can punched a hole in the side of the case (the thin ply common in the 70s & 80s), before embedding itself in the wall.

    The last one I had fail was only a small one - it sent a shower of paper and aluminium foil shreds round the room.
     
  14. eveares

    eveares

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    Sum vision; see photo below for specs.


    Also, this is the internals:


    Yes, for about the past 5 or 6 years stuck in the loft.


    Very wise indeed; I have just got a new GTX760 graphics card and need to upgrade my stock Channel Well Technology branded 450w psu. Think I will go for a EVGA Supernova PSU.

    I have to say, it is scary when a cap unexpectedly and catastrophically fails whilst making one hell of a noise and filling your bedroom full of rancid smoke.
     
  15. JohnW2

    JohnW2

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    Thanks for confirming. Electrolytics, particularly 'wet' ones, don't like that.

    Kind Regards, John
     
  16. RI1982

    RI1982

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    Sumvision just one about one of the worst brands, the Sumvision PSUs on Ebuyer etc £10 etc! I run an IT support business and wouldn't be able to sleep at night if I sold that rubbish to customers.

    EVGA sell some decent PSUs and a bit cheaper than Corsair etc.

    The specs are a joke too on that PSU, 26 amp on the 12v rail and supposed to be 600w! I bet it wouldn't have been able to cope with 15 amps.
     
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  17. 333rocky333

    333rocky333

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    On a similar vain, ive rcently had both a dvd player and a satelite box that were rarely used and on standby, in seperate incidents on turning on , they both went blank, the repair man said it was the dvd power supply. the satelite ive not bothered with.
    Is this a similar thing to the OPs, if so why does this occur.
    I actually have an electronics servicing city and quild, but to be honest I learnt naff all :)
     
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