Belton reverb tank went microphonic (relatively short lived)--this the new normal?

[dchang0]

I had a brand new Belton 8EB2A1B tank that I later removed the ground screw on the input side to turn it into an 8EB2C1B.

It sounded pretty good when new. But for whatever reason, after only very rare and infrequent use over the course of a couple of years, it started to go microphonic such that I can turn the reverb volume all the way down and still get reverb sounding like the knob is at a 5.

I know it's the tank because I can disconnect it and the reverb effect goes away. It's not microphonics in the tubes, in other words. I can also leave the tank connected and stick a rolled up cloth in the output end, damping/muting the springs, and the reverb effect goes away completely. It's like the transducer's glue or the spring dampeners came loose and it became supremely sensitive.

Is this normal for Belton and Accutronics? Is this normal for MOD? I'm wary of throwing money at the problem only to have the replacement tank die quickly too. (Why reward the companies for making crappy tanks by buying new crappy ones?)

Is there a way to fix the transducer like drip glue or wax on the coils or whatever? (Probably not worth the trouble--the wires are so thin I am probably bound to break them.)

Suggestions and experiences welcome--thanks very much!

[Chuck H]

Accutronics had some trouble once upon a time (shortly before they were absorbed) with some kind of damping material inside the transducer tubes. It was drying out and hardening prematurely and the tanks would become microphonic. I read (here I think) that the damping material they use to use became unavailable. I can't say about how this has gone with Belton, MOD or new Accu-Bell tanks except that I have used both Belton and MOD with some tanks over four years old and no trouble so far.

You mention microphonic in the thread title but the read seems more like the tank has become more sensitive or the output has increased. Are you having a ringing/feedback problem? If not I wouldn't complain. Reverbs are noisy circuits. The more input sensitivity and/or output from the pan the better for keeping the noise down.

If you DO have a microphonic problem I've had some luck tying a single strip of rubber band loosely around both springs near the transducers (maybe a figure 8 for your 3 springer).

[g1]

I can turn the reverb volume all the way down and still get reverb sounding like the knob is at a 5.
I know it's the tank because I can disconnect it and the reverb effect goes away.

That logic is flawed . Even if you set the reverb volume at 10 and disconnect the tank the effect will go away.
So what makes you think the reverb control itself is not dirty or faulty?

[Enzo]

Agree, I am much more concerned that you can turn the reverb control all the way down and still have reverb. That can't be the pan's fault.

[Jazz P Bass]

Which amp are we dealing with?

[dchang0]

Good point. I'll have to run some more diagnostic tests. Guess I'll start with measuring voltages at various points. Thanks to g1 and Enzo for catching that.

If it helps to diagnose, the amp did have some sort of weird sound like cloth being rubbed across a microphone grille prior to the reverb going microphonic. The sound went away on its own--I thought it might have been a loose guitar cable or something. I wonder if something burnt out. Nothing smells burnt, and there are no visible burned components.

Amp is a 5F1 with add-on tube reverb circuit I assembled myself. Fairly simple circuit--should be easy to diagnose compared with a lot of commercially-assembled amps.

[dchang0]

No ringing and feedback, and while the tank does seem more sensitive, it isn't louder, nor is it more sensitive when the reverb control is turned up. In fact, I would say the reverb when the control is 8 to 10 out of 10 is lower/less sensitive than when it worked properly. In other words, the floor got lifted, but the ceiling didn't lift up too, it actually dropped. So it's like the range from 1-10 got squeezed so that it's 5-7.

[dchang0]

FOLLOW UP:

g1 and Enzo nailed it. The reverb pot (made by Alpha) had gone bad somehow. A new Alpha pot works, but it also makes the light rustling noise when the amp is silent--I may need to buy a different brand of pots.

Anyway, the tank is fine, so my apologies to Belton for having jumped to the conclusion that it had gone bad.