Demeter TGA-3 having Volume Fluctuations...

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by jazzygeoff, Feb 25, 2006.

  1. jazzygeoff

    jazzygeoff Member

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    this a 100 watt version with a quad of SED EL34s and 6 - 12ax7. In the higher gain channel it is picking up radio interference as well don't know if that could be related. Just wondering if a input jack on either the FX loop or front of the amp could be acting like a open circuit?

    The volume fluctuation is intermittant, the amp sounds like god for the most time just the loss in volume or volume boost at inoppurtune times with no real loss in tone either way. Would any of you have an idea how to go about troubleshooting this?

    Thanks in advance.
     
  2. tga-3

    tga-3 Supporting Member

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    The front input jack on one of mine loosened up once and picked up radio stations too, just a little tightening up of the input jacks should do it. As far as the volume fluctuation, just give James Demeter a call. He's been very helpful several times over the phone. Once he had to jump off because Elvis Costello was on the other line!
    Then back to the "God-like" tones,
    Rick
     
  3. jazzygeoff

    jazzygeoff Member

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    Yeah I will give him a dingle.

    It Sounds like a old Fender Tremolo .... :confused:

    Checked my power cord from the amp to cab ok. Tried the amp dry no fx still does it. All the tubes glow normally, checked for microphonic pres' with the tap test ok,

    I guess a problem like this is not 'garden variety' then? I am still hoping it is something relativly minor. All I can see is possibly a crapped out condensor or solder joint on the output side, heck I was thinking that maybe a dirty or corroded tube socket could make it behave that way?

    I was just hoping that someone may have come across a problem like this in their experiences. Something that I could go on you know.
     
  4. brad347

    brad347 Member

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    a tube can glow normally and still be bad. You really gotta try the swap with a spare.
     
  5. jazzygeoff

    jazzygeoff Member

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    I'll start with the PI 12ax7 is that a safe bet? As this seems to effect the whole amp whatever channel it is on.
     
  6. jazzygeoff

    jazzygeoff Member

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    Ok, problem solved.

    I brought it in to the local tech and it was a cold solder joint for the power supply that was crapping it out. $50 tax in for the repair alls well that ends well.

    Thanks to everybody who offered advice.

    Geoff
     
  7. ericb

    ericb Silver Supporting Member

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    Wow, that is a great price as it's about the minimum bench charge for most guys, and a great deal that the guy found it! GOOD JOB

    ERIC
     
  8. jazzygeoff

    jazzygeoff Member

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    Yeah he said it took him less than a 1/2 hour to find it and another 1-1/2 to fix/clean up some little things and tighten up some loose pot and connector nuts. So obviously this guy 'Dan' is talented he works as a sub contractor for these guys. http://www.retrotownmusic.com/catalog/ :AOK
     
  9. brad347

    brad347 Member

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    it feels good to have a problem solved, doesn't it? congrats!
     

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