Do I need to replace this cap to sell my amplifier?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by wall_of_sleep, Jan 21, 2012.

  1. wall_of_sleep

    wall_of_sleep Member

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  2. stratman_el84

    stratman_el84 Member

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    It's hard to tell. Are there any similar brand/marking caps on the board to compare it to? I've seen new caps that have that look that are just manufactured that way. Try to ascertain by comparison whether it matches it's mates and try to determine if that's the way it was made. You might try looking it up on one of the online electronic parts supply houses like Mouser, Digi-Key, or Allied and compare the pics/drawings (you may have to look at the maker's datasheet for the part, usually a .PDF document link on the part listing/description blurb page).

    That's all I can tell you without more/better pics and more info.

    Good luck! :aok

    Strat
     
  3. JerryP

    JerryP Member

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    That's just the plastic cap that has warped. That does not mean the cap is bad.
    Jerry
     
  4. reaiken

    reaiken Member

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    Push down on the top and see if it is just the plastic that has deformed (from heat, or possibly made that way), or if actual pressure venting has started, pushing up the metal scored seal.
     
  5. wall_of_sleep

    wall_of_sleep Member

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    I'm not worried about the functionality. Everything seems good with the amp itself. I'm just questioning the odds of the cap becoming bad or spilling its guts onto the board in the future.

    The cap is a Samwha. The cap next to it is of similar make but different value. Of 6 of the same make caps on the board, this is the only one bulging. The amp is 20 years old tops.
     
  6. wall_of_sleep

    wall_of_sleep Member

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    This is over my head a little. What am I looking for in either event?

    I would compare this to pushing on a road bike tire. There's a touch of give, but it feels highly inflated.
     
  7. TweeDLX

    TweeDLX Member

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    Give will mean its just the rubber cap. A more solid feel means the vents in the top of the capacitor are pushing upwards.
     
  8. donnyjaguar

    donnyjaguar Member

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    Run the amplifier for a while and see if the capacitor gets warm. It should be at ambient temperature. If it passes this test and there's no hum from the speaker, I'm of the opinion its working fine.
     
  9. reaiken

    reaiken Member

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    The metal tops of some caps are scored so they will break open if the pressure inside builds up too high. They will usually push up a bit and then break open, unless they suffer a massive overload, when they will rapidly vent and spew tar and chickenfeathers everywhere.

    Some of them, particularly the smaller electrolytics, just depend on the rubber stopper at the bottom as a vent. These will usually launch the can a fair distance when they explode.
     
  10. Trout

    Trout Member

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    That cap looks pretty bulged, but the thing that sticks out in my mind,

    Conservatively speaking, that cap has pretty much reached the expected end of life anyway.
     

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