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GK MB150 shutting down. Help?

Discussion in 'Amps and Cabs [BG]' started by natemusic, Jan 13, 2005.

  1. I have a GK MB150 amp that's two years old, but hardly used in that time except at home. It shuts off all the time. It works fine with an extension speaker hooked up, but when I try and use it by itself, it shuts off within minutes. Any idea what this is?


    .... see last post for explanation, but this was easy to fix. Just checked some connections in the amp.
  2. Tritone

    Tritone Supporting Member

    Jan 24, 2002
    Santee, America
    Are you shutting off the internal speaker when you use the extension cab? If so, that would lead me to believe that the wires to the internal speaker have become loose and are shorting out. This could explain why the amp doesn't shut off when you plug in the ext cab.

    If you aren't shutting the internal speaker off, then I dunno.....
  3. I have tried it both ways, and it works fine, with or without the internal speaker turned on. As soon as the external isn't plugged in, forget it. Weird.
  4. Tritone

    Tritone Supporting Member

    Jan 24, 2002
    Santee, America
    hmmmm I would still be a little suspect of the internal speaker connection. The things are basically impossible to open up though, so........good luck :(
  5. Does your external speaker jack have a switch built into it?
    It sounds to me like the switch in the jack is intermittant and only works when you have a plug in the jack.

    Just a guess
  6. luknfur


    Jan 14, 2004
    I've thought about picking one of these thing's up and was struck by your comment. I understand they're aluminum chassis but what do mean they're "basically impossible to open up." Logically, if it has to be assembled then it comes apart. Apparently it doesn't have a the typically rear access panel, the electronics sealed?
  7. I had an older version (the 100 watt one) for years, quite a work horse. I eventually blew the speaker and opened up the amp (with some help) to replace the speaker. Well, it is impossible to get that thing back together. I eventually bought this new one. And now it's crapping out. I still think they are amazing, and don't know anyone else who has ever had problems, but because the amp is sealed, it's just a pain to open up and work on. So, this time I'll take it to a professional.

    For the size, they are really phenomenal, both for electric and upright.
  8. luknfur


    Jan 14, 2004

    somebody went of business fairly recently, can't remember if it was GK or who. But if not, what kind of warranty do those things have and have you contacted them about a probable cause?
  9. Tritone

    Tritone Supporting Member

    Jan 24, 2002
    Santee, America
    You're right, I guess I should qualify that statement. Last year, I was contemplating putting a "wizzy" type driver in mine. I couldn't not locate a single repair shop that would do it, because of (what I was told) the difficulty in opening the amp up. :confused: IIRC, it had something to do with the way they are final assembled. I could be wrong, but that's what I was told by more than one tech.

    OTOH, Mine is 14 years old and still running, and I can't count how many times the little critter has bailed me out. Great amp.
  10. luknfur


    Jan 14, 2004
    Yeh, I've had girlfriends a lot like that.

    At any rate, apparently these amps are relatively expensive to have worked done on that would explain why in part.
  11. Tritone

    Tritone Supporting Member

    Jan 24, 2002
    Santee, America
  12. try PM'ing Daniel Elliott. (one or 2 t's i can't remember), he's the GK guy on these boards. he'll get you set up...
  13. pjleo


    May 27, 2003
    del valley
    I have opened up the back of my gk 150 several times with no problem.
    There are maybe 20 screws. And also a sealer/gasket.
    I just used silicone to seal it back up.
    The reason i opened it was to experiment with some insulation.Which did not seem to make any difference that i could tell. I've had this amp aprox 10 years.
    good luck
  14. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    This could be wrong but I heard they are glued together, thus the difficulties in opening them and closing them back up.
  15. This one is a question for one of our techs. Call and ask for Arnel at the Factory.
  16. PhatBasstard

    PhatBasstard Spector Dissector Supporting Member

    Feb 3, 2002
    Las Vegas, NV.
    About 20 years ago I had the old version too (MB200 I think). No matter how loud or long I ran the thing, with or without extension, internal 12 on or off, the thing never crapped out, farted, or shut-down. Had it until 1990 when a big fall took it out of commision (I still mourn it's passing).

    Bought a new MB150 (the top model with all the bells and whistles) in about 1995. The thing went in to thermal shut-down very, very easy. Just the speaker outputs, the actual head stayed on and my line to the board stayed active.

    I don't think there was anything wrong with it, it just wasn't nearly as good as the old model. I sold it within two months as I was very dissappointed (as compared to my old one) as it was way too expensive for just a practice amp (as it was worthless for any actual gigging).

    PS. I only used these amps on low to medium volume gigs.
  17. Just to follow up. At Arnel from GK's suggestion, I opened up the amp (just the top, where the electronics are, not where the speaker is) and checked all connections by disconnecting and reconnecting. It works great now. I don't know what was wrong, but this fixed it.

  18. PunkerTrav


    Jul 18, 2001
    Canada & USA
    You've had 14 year old girlfriends? : :eyebrow: :p :D
  19. luknfur


    Jan 14, 2004
    Actually, I misread the post which resulted in my response. I tend to misread stuff a lot - but it's usually good for a laugh so I don't consider it a disability. Although it probably is technically. I know I'm dyslexic and I haven't heard of anything associated that tranposes phrases - but it exists for a fact.