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Thread: What is this cap?

  1. #1
    Supporting Member Randall's Avatar
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    What is this cap?

    I've got a Eden Metromix EM25 floor wedge amp in that was dead. I found the primary on the PT to be open, so I ordered a replacement, 8 months later it arrives and I pop it in. The secondary is 18.5v - 0 - 18.5v blu-red-blue on a three pin connector that can only be inserted one way. I fired it up and a little blue cap next to the connector (C52) burst into flames, smoke and soot everywhere.

    I took it apart and removed the charred pieces. The amp works without the cap, so I am wondering what is it's function? From resistance checks (I don't want to have to pull the board if I don't have to) I find one leg of the cap goes to one blue wire, and the other side of the cap goes to the other blue wire, so across the secondary. I don't find a schematic, so I wonder wht is the purpose of a cap across the secondary, and is it neccesary to replace it? And if this cap were leaking before, could this have taken out the primary?

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    It's weird, because it WAS working fine.....

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    Lifetime Member Enzo's Avatar
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    Do you still have the old transformer? If so, cut it open and see if your open primary isn't really just an open thermal fuse inside the thing.

    In any case, your cap was wired right across the secondary, so if it failed it was a dead short across that secondary. COuld that have caused teh transformer failure? Sure.

    Caps are often put across transformer windings for noise abatement. SOmetimes you see them on the rectifier instead, but same deal. I happen to have the Peavey Blazer158 open on my terminal, if you have that see C26 lower left. Same as yours except the cap was on the other side of the fuse. I also have the Peavey Bravo open, and again if you have that see both side of the transformer have caps C41, etc. I am Mr Peavey today, you must have a Classic 30 schematic. Both secondaries there have caps. C38, C51. Again same as yours other than a fuse was added.

    It is there for noise abatement. If you hear no objectionable noise, leave it out.

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    Supporting Member Jazz P Bass's Avatar
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    Not having a schematic for the EM25 I went looking at other newer Eden amps.
    It seems that they prefer .01 uf 250V capacitors across the secondary.
    WTB700.pdf
    If C52 was shorted or trying to short, that would certainly play havoc with the primary.

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  4. #4
    Bent Member Chuck H's Avatar
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    Quote Originally Posted by Jazz P Bass View Post
    Not having a schematic for the EM25 I went looking at other newer Eden amps.
    It seems that they prefer .01 uf 250V capacitors across the secondary.
    WTB700.pdf
    If C52 was shorted or trying to short, that would certainly play havoc with the primary.
    I was thinking the same thing. We tend to see similarities in design with the same maker so I went looking generally for Eden power supply schematics. Alas, I didn't find one with a reasonable search. If it were me I would install a .01u cap or, like Enzo said, if there's no detectable noise from the power supply just leave it out.

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    "Take two placebos, works twice as well." Enzo

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  5. #5
    Supporting Member Randall's Avatar
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    It is not making any noise, so I guess I am leaving it out. It's pretty quiet actually.

    And I wasn't kidding about the 8 month wait to get the transformer. I'm tired of looking at it, and want it gone.

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    It's weird, because it WAS working fine.....

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