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Thread: WTF? Why oh why is this amp humming?

  1. #1
    Forum Member memphisrain's Avatar
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    WTF? Why oh why is this amp humming?

    Just recapped my Gibson GA-5T. It had the funny old caps with all the wires going into the same end, so here is what I did.

    I removed the old cap and replaced with two caps with the same value. I wired both neg ends to the same spot and then wired one cap to each spot that the other one was in, thus putting them in parallel. I did this for both original caps, replacing the two original with 4 new caps.

    The thing buzzes like a MFer now. I've check all my connections and everything looks good. I tapped on all of the tubes and every cap and resistor in the thing. So now I'm stuck. Could it be that the caps are supposed to be in series? If so, how should I connect a one lead cap to two spots? Just make a jumper?

    Some help would be greatly appreciated...

    Oh... and please talk slow, I'm new at this

    Thanks
    :blbros
    If it has wheels, tubes or breasts....




    ..... You're going to have problems with it

  2. #2
    Forum Member Tele-Bob's Avatar
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    Re: WTF? Why oh why is this amp humming?

    Find the caps you took out and check them for polarity as they were in the circuit. Running those caps in series, vs parallel will change the way they work. If they're "electrolytic (polarized), they need to be installed properly. Even if they're non-electrolytic, there is a big difference between running them in series vs parallel.
    If you're bored, you're not groovin'.

  3. #3
    fezz parka
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    Re: WTF? Why oh why is this amp humming?

    Your amp requires 3 electrolytics to filter the b+:


  4. #4
    Forum Member memphisrain's Avatar
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    Re: WTF? Why oh why is this amp humming?

    So from that schem, I need two 10uf caps and a 20 uf cap, correct? If so I need to figure out where to connect them....

    Since I've already got 4 20uf caps, can I just use 3 20uf?

    Thanks...
    If it has wheels, tubes or breasts....




    ..... You're going to have problems with it

  5. #5
    fezz parka
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    Re: WTF? Why oh why is this amp humming?

    Yeah, I don't see why not. It'll be a little stiffer though, maybe o good thing for that little amp. Bleed those caps before going back in! Just follow the above schematic and you'll be fine.

  6. #6
    Forum Member memphisrain's Avatar
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    Re: WTF? Why oh why is this amp humming?

    Alright, one more question that may make my installation easier, Where should the 260,250, and 200 leads be heading to?

    Thanks..
    If it has wheels, tubes or breasts....




    ..... You're going to have problems with it

  7. #7
    fezz parka
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    Re: WTF? Why oh why is this amp humming?

    To the OT, power section, and preamp section respectively...

    Keep in mind that there are a ton of different versions of this amp out there. The voltages and resistor values could be a little different than what is shown in the schematic above. Did you draw a rough layout before you disassembled the amp?

  8. #8
    Forum Member memphisrain's Avatar
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    Re: WTF? Why oh why is this amp humming?

    Yeah, I did, but I can't seem to find it now, I'm a
    If it has wheels, tubes or breasts....




    ..... You're going to have problems with it

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