Leakage in Fenderish amp - channel two not silent

[überfuzz]

A while back I build an amplifier based on a Fender - Twin Reverb. Today I opened it up to tidy up the wiring. I worked mostly around the tube sockets, preamp. It seemed to work out fine, not that it lowered any noise, I think, but it looks nicer. However, when I had it all stitched up I had a go. I plugged in a guitar and played at low volume. Imagen my surprise, the amp played even with the volume at zero, min. I check more properly and it's only channel two behaving this way. The volume actually drops when raised from zero and between 2 - 3 there's a dip, not dead silence. From the dip to max it's behaving normal.

I don't know if the amp behaved this way before my tinkering. I figure I'll gut it again to see if I can pin point the leakage. Before I just like know if this is seen in Fender amp? The input wire is very long, could it be inducing signals into later stages?

When I have time to tinker I'll try to lift the signal wire to see if I can spot the issue. Any pointers before I do this..?

[Jazz P Bass]

I have noticed this before on tube amps.
It may just be the potentiometer not reaching zero ohms.
Ground the middle leg of the pot to see if that turns it off.
You may very well have a problem or the volume pot is just not squelching the signal.

[überfuzz]

I don't quite get it. Shorting the middle leg to ground will kill the tone if it's the pot not doing it's job properly... Or?

[JoeM]

I've had the same issue in my SFSR. Seems like some tubes in the V2 position are more prone to this than others. Try some different 12Ax7s and see if it changes.

[überfuzz]

Mhmm... I'll swap around the tubes. I've got some Ruby tubes and some JJ's in the amplifier.

[Mandopicker]

Ditto on trying a new tube.

[überfuzz]

It was a ruby tube, in v2, that miss behaved. I don't know... Where will I ever find nice tubes..? This amp seems a bit cranky.

[ThermionicScott]

Still sounds more like a problem with your pot, masked by some tubes but not others. What's the harm in a channel that doesn't completely "turn down" anyway?

Hope you're not actually throwing away working tubes over this.

- Scott

[überfuzz]

Hope you're not actually throwing away working tubes over this.

- Scott

Why no, they're safe... and sound. ;-) The leaking tube is sitting in the same place. It has got a nice sound. I think I'll test the pot when I get abround to it. Just to see.

[Mandopicker]

Most often it is not the pot...could be but not usually. In fact, just happened in my 67 BFSR...changed the tube and all is well. (Used a new JJ that was hanging around.) The volume pot was brand new, BTW.

Having said that...changing the pot will take about 15 minutes and you can know for sure. Been there done that.