Back to that noisy reverb

[Bob-I]

I thought that my buzz was caused by heaters, sounded like it, felt like it, wasn't it. I connected up a 6V battery, fired it up, still buzzes.

I process of elimination, I removed the reverb tubes and the buzz is gone. I then grounded the reverb return and put the tubes back in to eliminate the tank and wires, buzzes. I've already shielded all the signal carrying wires so I'm a tad stumped.

That gets me down to the reverb send/return. What to go for next? xformer? xformer position?

Other than this the amp sounds great. Any help is appreciated.

[MarkB]

I assume you've thought of everything I can, but... bad ground connection somewhere? Damaged wire, bad connection at the send/return? I think you're ruled out a bad cable shield.

[Bob-I]

I assume you've thought of everything I can, but... bad ground connection somewhere? Damaged wire, bad connection at the send/return? I think you're ruled out a bad cable shield.

Right after I checked out the heaters, I re-worked all the grounds. Since I grounded directly on the tube socket, I think I can eleminate a connection.

[Normster]

I process of elimination, I removed the reverb tubes and the buzz is gone. I then grounded the reverb return and put the tubes back in to eliminate the tank and wires, buzzes. I've already shielded all the signal carrying wires so I'm a tad stumped.

Does it still buzz with only one tube installed? With the tank disconnected? The only thing I can think of off the top of my head is the tank send should be as far away from the transformer as possible.

[Bob-I]

Does it still buzz with only one tube installed? With the tank disconnected? The only thing I can think of off the top of my head is the tank send should be as far away from the transformer as possible.

I'll check.....

yes... with the return tube in it still buzzes. Remove the send, no change.

Even with the tank removed and the return grounded it buzzes.

[Normster]

I know you're using a different reverb circuit, but Gary's circuit has a 220k grid stopper at the reverb return. Might be worth a shot to tack a 220k from pin 7 to ground on your tank return.

[jelle]

Hi
I had a problem with a Fender reverb unit which I did a point to point conversion. Also had a buzz. In my case it turned out that the reverb pan was not grounded although the send/return shields were.
One wire from chassis to pan did the trick.
Took me forever to find it out though...

I hope you find it!
Good luck,
Jelle
The Netherlands

[groovtubin]

Hi
I had a problem with a Fender reverb unit which I did a point to point conversion. Also had a buzz. In my case it turned out that the reverb pan was not grounded although the send/return shields were.
One wire from chassis to pan did the trick.
Took me forever to find it out though...

I hope you find it!
Good luck,
Jelle
The Netherlands

Man where were you last fall!! Actually TOOK OUT reverb on a build due to that crap! LOL!! Stuck in a D`ator, never looked back, have a DIAZ Classic twin thats awesome w/tube reverb in front of it, def like my Lexicon LXP-5 in my outboard D`ator better in the Dumble! LOL! Much thanks for the tip, thats def cool! Who woulda thought?

[Bob-I]

I know you're using a different reverb circuit, but Gary's circuit has a 220k grid stopper at the reverb return. Might be worth a shot to tack a 220k from pin 7 to ground on your tank return.

I have the 220k grid load in there. Thx.

Hi
I had a problem with a Fender reverb unit which I did a point to point conversion. Also had a buzz. In my case it turned out that the reverb pan was not grounded although the send/return shields were.
One wire from chassis to pan did the trick.
Took me forever to find it out though...

I hope you find it!
Good luck,
Jelle
The Netherlands

I'll give that a shot. This actually makes a lot of since, because the level of buzz changes with a different tank. I have one tank mounted in the head, and one on the bench for testing.

[Bob-I]

Hi
I had a problem with a Fender reverb unit which I did a point to point conversion. Also had a buzz. In my case it turned out that the reverb pan was not grounded although the send/return shields were.
One wire from chassis to pan did the trick.
Took me forever to find it out though...

I hope you find it!
Good luck,
Jelle
The Netherlands

I'll give that a shot. This actually makes a lot of since, because the level of buzz changes with a different tank. I have one tank mounted in the head, and one on the bench for testing.

Nope, actually it seems to be in the second gain stage after the reverb.

[mlp-mx6]

Could it be the shared cathode to ground, with other paths to ground in between? What if the V3b (the 2nd recovery stage) cathode had its own bias resistor (and optional bypass cap)?

I'm thinking the shared cathode is setting up a nice ground loop there, in parallel with the internal resistance of the tube, perhaps.

[Funkalicousgroove]

Are your reverb send and return jacks isolated from the chassis? I had a reverb with a buzz that wouldn't go away in a Twin Reverb and I ended up having to isolate the Jacks from the chassis using fiber washers, then I ran a bus between the sleeves of both jacks and grounded that point at the cathodes of the reverb tubes and it was quiet as a mouse. The orientation of your reverb trannie could have an effect on buzz too, try to keep it at a 45 degree angle to the tubes ala Fender.

[Bob-I]

Are your reverb send and return jacks isolated from the chassis?

No... but I tried it and there was no change. Remember the problem is in the SECOND gain stage of the return, not the first.

The orientation of your reverb trannie could have an effect on buzz too, try to keep it at a 45 degree angle to the tubes ala Fender.

Again, I tried moving the xformer. It's at a 45 degree angle but I removed the bolts and turned it, no change. Damnit.

Thx.

[Bob-I]

Could it be the shared cathode to ground, with other paths to ground in between? What if the V3b (the 2nd recovery stage) cathode had its own bias resistor (and optional bypass cap)?

I'm thinking the shared cathode is setting up a nice ground loop there, in parallel with the internal resistance of the tube, perhaps.

Well, I tried it, no change. Damn this is frustrating.

[Funkalicousgroove]