Tremolo ticks on my vintage amp. Help please.

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Lost_Cause, Dec 20, 2009.

  1. Lost_Cause

    Lost_Cause Member

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    I have a 69 Gibson Duo Medalist that is a two channel all tube amp with channel 1 having Reverb and Trem. The tremolo sounds great but it makes an faint audible tick when it oscillates when the speed is between 0 thru 7 ish. When you play it can not be heard. It is pretty faint. I have changed tubes and no change. There is a light that also turns on and off with the oscillation of the tremolo. Also, when I turn off that circuit via the footswitch the sound stops.

    First, is this typical of amps with a tremolo circuit? Is this a symptom of it being vintage perhaps? Is there anything that I can do to eliminate it? Might a recap of that circuit be necessary or something like that?

    If anyone had any insight I would appreciate it if you could help me out. The amp sounds killer and the tremolo sounds great but when not playing you hear a faint tick tick tick as the light flashes on and off.

    Thanks in advance for the help.
     
  2. Lost_Cause

    Lost_Cause Member

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  3. gldtp99

    gldtp99 Member

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  4. Lost_Cause

    Lost_Cause Member

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    Thanks, I can check only one out of those. The signal wire. It is point to point not PCB or turret board. I have not found much on line that is not Fender specific. It is not bad so I pretty much live with it but wish it would stop.
     
  5. brad347

    brad347 Member

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    I know what's causing the problem. It's the light that turns on/off with the oscillation. This is an optical tremolo, like a blackface or silverface Fender.

    When the light turns on, it dirties up the power a bit and causes the ticking sound.

    There are a couple of things you can try. One is that you can try a weaker tube (not a newer/stronger one) in the oscillator spot. This might make the light not want to turn on as 'hard.' I've never done this myself (I only have one amp with an optical tremolo, and I live with the ticking, as it's rare that I have the tremolo switched on), but perhaps a slightly lower-mu tube like a 5751 would help? Would be worth a shot if you have one laying around.

    Another would be to fashion your own optoisolator "roach" using an LED instead of the neon lamp. Perhaps there is even a suitable LED-based opto on the market you could find and re-purpose for your needs. In my experience, the "ticking" with a neon-based optical tremolo is just a fact of life. You either live with it, find a delicate workaround, or go LED.
     
  6. Lost_Cause

    Lost_Cause Member

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    The light is large one piece rectangle and it is wired into a harness that runs down to the lower chassis.

    There are two tubes that could possibly be the culprit. I will need to look at the circuit again and see what subs can be used. I want to say that one is a 12au7 and the other is a 6EU7.

    Thank you very much for your help. At the very least I have an answer as to why it is doing that and what might be required to fix it. It is not that bad.
     
  7. brad347

    brad347 Member

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    I had a look at the schmatic. It's interesting... there's a lot going on.

    The tremolo oscillator is a 6EU7, V4.

    What makes it interesting is that there are TWO lights... one is a visible indicator, and the other is hidden in the photocell. Either/or/both could be causing the noise.

    Maybe a weak 6EU7 would help? the indicator lamp... you say it's a one-piece rectangle... is it neon? Incandescent? Not sure? LEDs were invented in 1962 so even that is possible...

    As for the photocell, look for it and see if you can see a blinking light when the tremolo is on. Turning out the lights in the room might help. If it's a little orange blinking light, then it's definitely neon like the Fender style.
     

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