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Possible capacitor identification.

Discussion in 'General Electronics Discussion' started by Logi Devon, Jan 21, 2016.

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  1. Logi Devon

    Logi Devon

    4
    0
    Jan 21, 2016
    Hi Guys

    I accidentally plugged my surround sound from America into a UK outlet without putting it through a step down transformer and it blew what I think might be a capacitor, I unfortunately don't have a circuit diagram, if anyone can help me identify this red part it would be amazing, I've also included 2 pics of the area it came from in the circuit.
     

    Attached Files:

  2. 73's de Edd

    73's de Edd

    2,993
    1,261
    Aug 21, 2015
    .

    Sir Logi Devon . . . .


    You makee everything go boom-BOOM!

    You have just discovered an AC line, metal oxide varistor, put there to capture and blunt out short ac line spikes.
    But in your case of such severe-severe abuse, they just 'splodes.
    For your line voltage I usually expect a 130 v unit on upwards to a 150 V unit.

    Reference:
    http://www.digikey.com/product-detail/en/V150ZA20P/F1940-ND/1009285

    You know about the fuse but also look for any produced conductive carbonization of the PCB in that immediate area.


    73's de Edd
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,448
    2,809
    Jan 21, 2010
    That's a varistor. It is designed to absorb the energy in voltage spikes to protect your equipment. In this case it couldn't handle half the power in the entire UK power grid, so it expired.

    The question is now what else failed?

    I would expect the fuse also blew. The first thing I would try is to clean up the mess on the board with some isopropyl alcohol, replace the fuse, and connect it to your transformer before switching it on again.

    If it works, you have been hit by the lucky stick. The varistor is not absolutely necessary, although I would replace it.

    If the fuse immediately blows in a very vigorous manner then it is likely that a rectifier has failed short circuit. This will need to be replaced.

    Depending on the arrangement of the circuit, several other things could have blown, but let's try the simple stuff first.

    Also, one thread per topic is sufficient.
     
  4. Logi Devon

    Logi Devon

    4
    0
    Jan 21, 2016
    Thats great, thanks a lot for your help, and yeah 73s it did go boom, massive bang and i realised what i had done.
    If I was to replace the fuse and use my step down transformer what varistor should I buy to replace the old one?
     
  5. 73's de Edd

    73's de Edd

    2,993
    1,261
    Aug 21, 2015
    .

    Sir Logi Devon . . . .


    I initially placed the URL for your reference, but by your being in the UK a good preference would be NW of London at High Wycombe at Mousers, with their no minimum order and reasonable shipping.

    Like I said, use a unit with an AC voltage spec rated between 130 V on the low side or up to 150V on the high side.

    Looking at exactly what original manufacturers actually buy, consider this most POPULAR size and rating, of which they are stocking in excess of 10,000 of them.

    http://www.mouser.co.uk/ProductDeta...EpiMZZMv1TUPJeFpwbiZv6F%2bB5%2bGmJ6AmWlkHUTI=

    73's de Edd


    .
     
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