Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Baguette on February 19, 2011, 05:48:46 am

Title: reverb TANK buzzes
Post by: Baguette on February 19, 2011, 05:48:46 am

So I've made this AB763 style amp. Reverb is a bit different since it uses a capacitor driven tank, but insertion points are the same as an AB763.
I get a huge buzz when I turn the reverb knob up. Not a low hum like 60hz, but a nasty bzzzzzz.
So much the verb is unusable

- when I disconnect the tank output, I get a clean white noise when I turn up the verb.
> I guess my circuit / less dress is good.

- when I disconnect the input of the tank, and connect the output, it buzzes no matter what
> I guess the reverb driver circuit is ok.

I tried another identical tank (TAD 4FB3D1B) but it still buzzes. Tried another reverb cable, still buzzes.
The tank is in the correct orientation (output far from PT).
The bzzz is still here when I get the tank out of the cab and move it around.
BTW the stock tank has insulated input and output but I grounded the output to make it like a 4FB3C1B.

I'm totally out of ideas.

What should I do to quiet down this tank?

Thanks for helping out!

Title: Re: reverb TANK buzzes
Post by: LooseChange on February 19, 2011, 06:21:15 am

Move the tank around and see it it stops... Check your grounding. Clip a ground from the amp to the tank. Anything?

Title: Re: reverb TANK buzzes
Post by: 67polara on February 19, 2011, 08:54:34 am

I had the same problem had to turn the tank 180 to get it away from the transformer.  After that got dead quiet.  Guess this happens all the time need to get it away from the transformers.

Tony