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GK 400 rb volume fading in and out

Discussion in 'Amps and Cabs [BG]' started by Sharpie555, Apr 20, 2017.

  1. Sharpie555


    Nov 27, 2007
    So I screwed up and didn't realize the amp was on. I removed a compressor from the effects loop, the amp made a loudish pop and then made no sound. I turned it off and on and now it makes sound but the volume fades in and out while I'm playing. It's a mid 80s GK 400rb. How bad did I screw up? Is it fixable or should I be amp shopping? Thanks in advance for any help.
  2. wave rider

    wave rider

    Jan 5, 2005
    Jumper the effects loop with an instrument cable. Very common for a little bit of corrosion in the jacks to cause that behavior.

    funkytoe likes this.
  3. funkytoe

    funkytoe In Memoriam

    Jan 17, 2008
    Northern California
    That is exactly what I was going to suggest. Or just shoot some contact cleaner like deoxit on a 1/4 inch cable and insert it into your amp's send and return jacks on the back of the amp. As wave rider said, these sometimes corrode and have trouble opening and closing. Makes it sound like the amp is cutting in and out. Luckily its a quick and cheap fix that has saved many a 400RB and 800RB from the scrap heap.
    wave rider likes this.
  4. BassmanPaul

    BassmanPaul Inactive

    This does not address the problem of the switching contacts in any way. Too much contact cleaner just sprayed into the amp can cause more problems than it solves.
  5. a good point, but to be fair he did specify to spray the plug rather than the jack.
  6. This is what the effects return jack looks like. See the nipple on the bottom, this is what connects your signal with nothing plugged in. See the signal flow.


    When a plug goes in the nipple is lifted, breaking that connection and the signal comes from the cable.


    To properly clean this jack you need to clean the nipple. Spraying the hole or putting it on the plug will not reach it.

    I do not know if this will fix your problem, but this is how to clean this jack.
    TBGFRED likes this.
  7. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

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