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Problem with used GK MB Fusion 500

Discussion in 'Amps and Cabs [BG]' started by grinx, Oct 16, 2017.

  1. grinx

    grinx Supporting Member

    Mar 24, 2003
    Raleighwood, NC
    Bought this used a month or so ago here on the Xfieds
    Didn't try until last week
    It was awful.

    using A controls only, at low volumes (under 9 o clock settings) playing one note it sounds fine.
    turn the volume/gain above 9:00 it starts breaking apart
    play 2 notes together (power chord) at low volumes it breaks up

    I plugged a cable into all of the jacks 50x each
    There is no crackling from any of the knobs

    Used speakon and 1/4
    Used same speaker (GK Neo 112-II)
    Tested against a GK 400RB-III with and without a secondary preamp. No breakup

    It isn't the speaker
    It isn't the cables

    Next steps?

    Thanks all
  2. What exactly is "this"? If you posted a pic., sorry I don't see it.
  3. Fix broken amp.
  4. BassmanPaul

    BassmanPaul Inactive

    Quick test that cures surprisingly many such problems is to link Effects Loop, if it has one, Send and Return with a signal cable. Same for Pre-amp Out and Power amp in.
    Old Garage-Bander likes this.
  5. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

    I bought one from GC that was the same way. I returned it & they put it right back on the sales floor. Yes, I explained the problem to them, but they didn't not care, at all!
    Finally it turned up at another GC & they dropped the price to less than $200 "as is".

    I assumed the tubes had a problem, try changing them.

    Is that what you did with the RB, bypass the preamp on the MB?
    That would give you an indication if the fault lies within the preamp.

    To be more clear,,,
    run a patch from the RB effects Send to the MB effects Return
    plug into the RB & see how the output of the MB sounds
  6. 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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