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Ampeg TM1 replacement *help*

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  • Ampeg TM1 replacement *help*

    Hey guys,

    I was fixing a weak trem, which worked perfectly but was just too faint for some of my keys and the speed was also losing it's flavor. Got the new tm1 in and... nothing. Well, I get a volume drop when I turn the intensity knob now which never happened before (maybe because the trem was weak) But when I hit the trem switch, instead of trem, it's just volume drop, until I switch the pedal off... I get a brief second of trem before the pedal is fully disengaged. Hmm.. Are the neons backwards?

  • #2
    old tm1
    https://ibb.co/mDsRsMW
    new tm1
    https://ibb.co/XWTr16p
    demo of new tm1
    https://streamable.com/8edemr

    Comment


    • #3
      Is the oscillator working? If not, you sometimes get this kind of result.
      "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

      Comment


      • #4
        The oscillator circuit has to be working if the trem was oscillating before I changed the tm1, no?

        Is the oscillator the 3 green .47uf 400vdc caps? I could change those if the old one worked but was faint I'm confused at why it doesn't work, but is strong when the switch is almost off...

        Comment


        • #5
          The oscillator circuit has to be working if the trem was oscillating before I changed the tm1, no?
          Doesn't matter what it used to do when it worked, it doesn't work now, so we cannot assume the oscillator is oscillating. Never think up reasons not to check something.

          The three feedback caps either oscillate or not, in general I wouldn't think them the cause of weak trem.
          Education is what you're left with after you have forgotten what you have learned.

          Comment


          • #6
            Enzo, so true. I appreciate the philosophy. I have 3 new caps I will replace with now.

            Comment


            • #7
              Update.

              Replaced all the caps in the trem circuit with the fliptops kit and while I have louder tremolo, it is definitely worse tremolo.. It is acting sporadic and finicky... Trem goes completely silent if either speed or intensity are lower than 1/2 and with intensity up, speed doesn't work until it's at 1/2 and already pretty fast. Here is a video of it doing some weird stuff all on its own. I'm debating if I should put the old tm1 back in.

              https://streamable.com/n3ano2

              Comment


              • #8
                The usual problem with the caps failing is they leak DC and the oscillator won't start, or becomes intermittent at starting. Changes in value affect speed, but have no affect on anything else. What amp is this?

                EDIT: See here for more TM1 info;
                https://music-electronics-forum.com/...olo-module-tm1

                Comment


                • #9
                  Mick, the electrolytic caps around the trem circuit have been replaced as well as the .47uf film caps. The video link in my last response is fully updated with new tm1 and trem kit. No caps were leaking and the trem worked before, much softer, but worked. Wondering why it is being so bizzare.

                  Here it is with a view of the controls..
                  https://streamable.com/5qu367

                  Comment


                  • #10
                    It sounds like it's stuck on after-beat? Wondering how that could be. Tremolo/after-beat worked normally before replacing with the kit. Wonder if it's possible the leads for the photocell connecting to the intensity pot were backwards from what the description said... don't see how that would do anything though.

                    Comment


                    • #11
                      The photocell isn't polarized, just like a regular resistor. Double check the polarity of the cathode bypass cap and take a look at the tube DC test voltages on the schematic. The plate voltage should be 190v trem off, 125v trem on. Cathode voltage 2.7v off, 1.2v on. Your DMM will show the modulated neon signal unless you have a scope - at least well enough to see that it's working (this is where an analog meter works well). You need to establish whether the neon is getting its modulation voltage under all control positions when the trem is on. If it is, then the fault lies in the photocell-side of the circuit.

                      Comment

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