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Ampeg GU-12 build and tremolo not working

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  • Ampeg GU-12 build and tremolo not working

    I've gone over and over the drawing, been taking resistance readings through sections of circuits, looking for missed or incorrect connections and keep hitting a dead end. are there any mistakes in this schematic in the tremolo section?

    One thing that does look odd in the drawing is that next to the bass pot there are 2 ".01" labels but only one symbol for a cap. Is there supposed t be another symbol for a cap or is it supposed to only be 1 ".01" label?

    Amp sounds fine and reverb works. The amp is very quiet (no/little hum) but will begin making a bit of hum if 1) the treble pot is at anything but zero 2) the volume pot or master volume (lar/mar) are maxed or close to maxed and the hum will pulse at the rate of speed set by the speed pot but the intensity pot seems to have no effect at all on the hum or guitar sound. The master volume is the only deviation from this drawing.


    I'm starting to grow tired of debugging circuits that I'm not familiar with. I think from this point out I'm going to start doing a select few circuits and improve upon those and then add a new circuit to the arsenal every once in a while. Until this point I've been building just about anything people ask me to build and it's been great and I've learned alot but it's time to hone it down into about 5 amps or so that I can call mine and get to know those circuits completely inside and out and improve on them as time goes on.
    Attached Files
    ~Semi-No0b Hobbyist~

  • #2
    It might also be worth noting that the tremolo triode has an oscillating plate voltage and cathode voltage. Drawing shows 95v and 1.45v and I'm getting (with speed maxed) 100-130v and 1-1.3v, so a little high on the plate and perhaps a little low on the cathode but still in the ballpark.
    ~Semi-No0b Hobbyist~

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    • #3
      Mort,

      If you can peg this one down, I think you could have a serious hit... It <NAILS> period Stones. I had one and my buddy blew it up. Of course, that was the days when I didn't know what I was doing. Wish I'd sat on that busted amp... Nothing helpful technically, but in my opinion, this one is worth it. I could even do without the verb.

      Justin
      "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
      "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
      "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

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      • #4
        I think I may have just figured out the problem. I used a Fender style LDR but the drawing shows CL1110M and at fliptops website that's a whole different part with a whole different price lol.

        Good thing the customer is an amp builder and supplied most of the parts and will buy it and have it sent to me
        ~Semi-No0b Hobbyist~

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