Tube Amp Problem!

Discussion in 'Amps and Cabs [BG]' started by stevekim, Mar 30, 2003.

  1. stevekim


    Feb 11, 2000
    los angeles, ca
    I need help. My Mesa D180 cuts out at high volume. I have replaced both speaker cables, checked both of the mesa 1x15 cabinets i am using, put in brand new mesa power and preamp tubes, sprayed the jack on both the amp and cabinet with contact cleaner. Anyone know why this might be happening? I plan on taking it to the tech this week but since this only happens when playing very loud i am afraid they might miss it. I had actually taken it in before for the same problem and was told it was working 100%. if it helps, my settings are as follows:

    master: 10
    volume 2:7

    graphic eq: slight boost at 100 and moderate cut at around 600hz.

    the symptoms:
    amp will sputter, sudden loss of power then complete loss of power. the amp starts to behave VERY erratically. i will play hard but the sound coming out will be very quiet, then all of a sudden the sound will cut back in very loud again. there is usually some pretty nasty sounding distortion associated with all this.

    Thanks. I would really appreciate any help from you tube gurus!

  2. sounds like your preamp is about to fry, bring it to a different tech to look at
  3. My guesses: a) bad solder joint somewhere
    or b) coupling capacitor going south. I've had similar symptoms with either problem.

    The coupling cap should be easy to find if the amp is kept under load long enough for the problem to manifest itself again. Then the tech can measure voltages on the tubes until he finds the culprit--that's how I found mine. Though this is not recommended for the beginning do-it-yourselfer to try since the high voltages inside a tube amp can kill.

    Once the bad cap is found (or a bad solder joint) repair is simple. The frustrating thing is finding the intermittent problem. Good luck.
  4. dufus1478


    Mar 26, 2003
    Yeah, sounds like a solder problem. (cold solder). I'd check your input jack (jiggle back and forth) or effects loop.

    If all else fails , you can try a service center ,dealer or manufacturers.

    Check out the web site
  5. stevekim


    Feb 11, 2000
    los angeles, ca
    thanks for the replies everybody. i plan on taking it to the mesa boogie store but i wanted to get some ideas on what it could be so i can tell them to look into it. i had it in there a month ago for the same problem and they gave it a clean bill of health so i'm thinking it might be something small and easy to overlook.
  6. I had the exact same problem with my Carvin 600. Took it in to the tech and he found that the send return jacks were rusted and causing it to cut the signal.. He took them out cleaned and lubricated them and fixed the problem..So you may want to have them check those jacks........