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Does time or use cause the caps to degrade?

Discussion in 'Shock Brother's DIY Amps' started by AllenR, Feb 28, 2012.

  1. AllenR

    AllenR TDPRI Member

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    I have a 1964 Ampeg SB-12 that hasn't been used in decades. So I took it to Dennis Kager at Central Jersey Repair and had him go over the amp. Besides changing the plug to a 3-prong, the report came back with the amp in very clean shape and with a suggestion of putting in a set on NOS tubes (old ones were only putting out 20wts).

    I asked about the capacitors and he said they were fine. I forgot to ask what causes them to fail so does anybody know? I was suprised it didn't need them replaced.
     
  2. jefrs

    jefrs Doctor of Teleocity

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    Using the capacitors keeps them healthy.

    Leaving them idle lets them deteriorate, but they can often be re-formed.

    Easy enough to test on a capacitance meter. If they ain't bust don't fix them.
    They do go down and when they're bad they're horrid.
     
  3. telex76

    telex76 Doctor of Teleocity

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    +1, this.
     
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  5. celeste

    celeste Friend of Leo's

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    Electro's most common failure mode is an increase in ESR. If you don't have an ESR meter, then you have no idea. A capacitance meter alone does not cut it. If you fix switch mode power supplies, one of your mandatory tools is an ESR meter

    Using an electro keeps the oxide dielectric in good condition, and as jefrs says they can be reformed IF the acidic jelly electrolyte has not dried out.
     
  6. BobbyZ

    BobbyZ Poster Extraordinaire

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    I have a 62 Ampeg to recap this week. It hums I'm doing a recap. Since it works I'm thinking the tone caps are fine but all the E caps are going in the trash can.

    I'm one of those just recap it guys. Seen too many leaking filter caps to screw with testing them.

    Did my SFSR this summer had it for 10 years play it alot the filter caps started bulging. So even playing them alot sooner or latter thay can go bad.
     
  7. celeste

    celeste Friend of Leo's

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    There was a major rash of bad caps about 10 years ago. It seems that only like 3 companies make he electrolyte, and one of them changed their formula.
     
  8. Rich_S

    Rich_S Friend of Leo's

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  9. celeste

    celeste Friend of Leo's

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    I don't recall them being, but most of the big name American and Japanese makers were.
     
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