GK MB212 Problem - Any Suggestion?

Discussion in 'Amps and Cabs [BG]' started by beam2611, Jul 11, 2018.

  1. beam2611


    Jan 14, 2010
    Montreal, Canada
    Hey guys,

    Long time GK user here, in the past I owned 2 RB800 and a RB700.
    Now have a MB212 for portability.

    I love how the GK MB212 usually delivers on various gig settings.
    However yesterday when I turned it on during soundcheck at a venue.
    It only played at 5% of the expected volume when gain & master volumes were set at 12 o'clock, same as usual, sometimes lower.
    Check it again this morning, same thing. Sound like a 10 watt amp.
    If I turn up the gain, boost & master volume I get a little more volume but a lot of hiss.

    I have a soundcheck this afternoon and another show tonight.
    Is this an issue anyone else has experienced?
    Is there a way to sort this out quickly?

    PS: tested with various cables and basses, those were not at fault.

    Any suggestion would be welcome.
  2. kpc


    Apr 6, 2011
    Notify GK.
  3. beam2611


    Jan 14, 2010
    Montreal, Canada
    I have, thx
  4. Kro


    May 7, 2003
    New Jersey
    Sorry to hear about that, terrible timing.

    Aside from the testing that you've already done, I'm not sure how much is left to do aside from taking it to a tech.

    I have experienced issues with my MB amp (not a combo) in the past, but nothing like what you're describing. The types of failures I've experienced are those that tended to put the amp in safe-mode.
    beam2611 likes this.
  5. BassmanPaul

    BassmanPaul Inactive

    Effects loop jacks can cause this sort of issue. If it has one, link Send and Return with a short signal cable to see if that helps.
    alaskaleftybass and wave rider like this.
  6. Thornton Davis

    Thornton Davis

    Dec 11, 1999
    Unfortunately Paul, the GK MB Combos don't have a send and return so beam2611 is going to have to rely on either GK directly or a local amp tech to diagnose and fix the problem. I suggest he take it to the closest L&M in Montreal.

    Last edited: Jul 12, 2018
    agedhorse, beam2611 and BassmanPaul like this.
  7. Wasnex


    Dec 25, 2011
    Did you check the -10dB pad on the front panel?
  8. beam2611


    Jan 14, 2010
    Montreal, Canada
    Bought it second hand, Just realized I got a first Gen MB212.
    No fx loop. no -10db Pad.

    However, I got a lead on a good guitar amp repair tech. He says he's dealt with the GK amps issues often. He thinks it's either the pre-amp or output section. Going to see him tomorrow.
    Count Bassie, scuzzy and Wasnex like this.
  9. BassmanPaul

    BassmanPaul Inactive

    Your amp contains three basic sections. Pre-amp, power amp and power supply. Two out of three ain’t bad! :D