fender reverb feedback

[txbluesboy]

I built an amp for a friend that is basically a Fender Deluxe circuit in a Princeton combo cab, using some leftover Tone Slut TW style transformers. It has really proven to be an awesome amp in a small package (6l6's and a 12 inch Celestion). It worked great for about a year then developed a problem with the reverb feeding back. I went through and checked all the grounds and added coax to the reverb tube grids but can't seem to get a handle on it. Any ideas?

[selloutrr]

did you check the tube?

[FUCHSAUDIO]

bad tank

[M Fowler]

The little transducer wires inside the reverb tank break.

[txbluesboy]

Thanks, but changed the tube and tried a different tank.

[Milkmansound]

definitely make sure there is not too much gain on the recovery side of the reverb. I have made this mistake in some of my experiments and caused feedback that way. You might want to add a voltage divider consisting of 2 220k resistors before the PI to emulate the load of the second channel.

Double check the wiring too - never hurts.

[txbluesboy]

Thank you for your suggestions everyone. I tried the 220K/220K divider you recommended and it did remove some squeal at high reverb settings, but the feedback was still there. I added some padding around the tank before sliding it back into the bag and that fixed it. I remember wrapping thick paper towels around it when I built it now. The customer, thinking that didn't look normal, removed them apparently when he had the amp apart to recover it.

[tubelectron]

I added some padding around the tank before sliding it back into the bag and that fixed it

As usual !!!

See below the padding that I have done for my Boogie MKIIA, among other amps :

original situation :

[img:640:480]http://img11.hostingpics.net/pics/436299IMG8371.jpg[/img]

padded situation :

[img:640:480]http://img11.hostingpics.net/pics/545663IMG8389.jpg[/img]

I just used old blue-jeans and wollen pull-over sleeve cut to size : perfect...

A+!