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GK MB500 -- has anybody seen this failure mode?

Discussion in 'Amps and Cabs [BG]' started by RHFusillo, Dec 13, 2013.

  1. RHFusillo

    RHFusillo Supporting Member

    Mar 20, 2000
    Phoenix, AZ
    I have a Gallien Krueger MB500, purchased about 18 months ago. Today, the amp failed and I cannot find anything on the web that describes this problem.

    The amplifier produces no sound. The "halo" pilot light that surrounds the on/off switch is dark, even when the switch is pushed in. The "-10 db" switch is lit solid red, whether that switch is pushed in or not.

    I powered the unit completely off and left it for about an hour, but the same thing happened when I tried to power it back on.

    There is no weird smell that would indicate fried electronics.

    I figure that I will have to send the amp back to GK for warranty repair, but I am curious about how serious the problem is.
  2. B-string

    B-string Supporting Member

    Have you unplugged it, let it sit and tried a different outlet? Unplug the speaker cable incase it shorted? I would imagine it would have to be a power supply (SMPS) failure.
  3. RHFusillo

    RHFusillo Supporting Member

    Mar 20, 2000
    Phoenix, AZ
    Thanks for your reply, B-string. The answer to each of your questions is yes.
  4. B-string

    B-string Supporting Member

    Sounds like a random failure in the units power supply then. Most good SMPS will self check when plugged in and not latch "on" if a failure is detected (protects other parts of the amp). Contact jason@gallien.com for an RMA and shipping instructions. :atoz:
  5. rajprods


    Nov 22, 2011
    The exact issue you described happened to me in the middle of a gig last Saturday. Can you state what the issue was? Did it happen again after it was repaired?