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GK MB210 Combo Not Working [help?]

Discussion in 'Amps and Cabs [BG]' started by Stev187, Jan 19, 2012.

  1. Stev187

    Stev187 Peavey MegaBass Club!

    Jan 11, 2011
    Toledo, OH
    Hey gang. I think I know how this story ends, but I thought I'd ask anyway.

    My son and I share a GK MB210. We like it. My band practice is the night before his, and I left the amp in the trunk of my car for about 48 hours. It's been pretty cold here (below freezing) but the trunk is dry and the amp hasn't been wet. I never leave instruments in cold vehicles, but I've never had a problem leaving solid state amps in the cold.

    Tonight for his band practice, the amp wouldn't power up. Nothing. Luckily his buddy had an amp to play through. I purchased this unit used, so there's no warranty. I pulled the amp out of the cabinet (this is very easy to do) and inspected the fuse. It's not blown. Meter shows power getting beyond the switch, etc. I've let the unit warm up and dried it with a warm (not hot) hairdryer. Nothing.

    So, looks like this is going to a tech. But I thought I'd ask to see if there might be some other thoughts before I take it in. I suppose it's possible that the time spent in the cold is unrelated to the failure, but I imagine they are connected. The only thing I can think of is that some condensation shorted something out. Would that go away once the unit dried out, or would it be permanent? There's no sign that there was any moisture in the unit at all.

    Let me know you're thoughts. I'm pretty bummed now that both of us are each in a band using this thing. THANK YOU!

  2. Could have a cold solder joint and the cold finished the fracture of the joint. Contact brian@gallien.com see if there is something he can do for you.
  3. Stev187

    Stev187 Peavey MegaBass Club!

    Jan 11, 2011
    Toledo, OH
    Thanks, B-String. I went over the whole thing with our electronics faculty, and it's not a cold or broken solder joint. There is a temperature sensor attached to the heat shield with a zip tie. It's an LM35CZ and the leads are broken. So no matter what, that guy needs replaced.

    The puzzling thing is that we get no red light failure. Nothing. With this temp sensor down, would you expect the whole thing not to power up? Anybody have experience with this?

    No local source for the LM35CZ, so I need to order it. I'll post back here with results... but if anybody's been down this road and can tell me what they know, I'd be happy to hear about it.

  4. I don't have schematics for the MB series but if the temp sensor is tied into the switching supply it is perceived as -40 degrees f.when open. Might inhibit a power good signal from the power supply?
    G-K Parts
    or (209) 234-7300 extension 120. 9am to 4pm PST USA
    Calling is best, Lany is a very nice person. :)

    Also have this link http://www.mouser.com/Search/Refine.aspx?Keyword=LM35CZ

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