Valve Jr-5e3 clone build 2nd volume oscilliation

[greenhorn]

Hi guys,
Well its been a while and now that the fall weather is here I was able attempt a finish of my 2nd 5e3. I get no time in the spring and summer..then finally its cold and the nites are indoors.
 
I gutted my valve jr....I know...How could I? Anyway, This build utilizes a pt from a hammond L100, Hoffman board,Triode output tranny,  and the chassis of the valve jr head. Pretty tight fit, but I made it.  Its pretty much stock circuit,but I changed some cap values (which I found on old posts-thanks geezer) to give it a little headroom for 6l6's and reduce the boominess.

The thing was working beautifully until I added a 2nd volume.
It still sounds great with the 2nd volume down to zero. But as soon as I turn it a little....I believe it starts oscillating. Anyway the sound is similar to feedback, but low. Its increases with 2nd volume. any thoughts. I used Doug's layout for the build. Thanks ahead for any pointers.
Charles

[stratele52]

IMO you have bad wire dress.

Your pictures are too small to bee usefull, but I see a red shielded wire with the withe wire too long unshielded end. Also your other volune need alo a good installed shielded wire.

Remember all signal wire act like antenna you need proper installed shielded wire.

[Geezer]

Agree....prob lead dress.

Get the thing oscillating then chopstick (move around with a non-conductive probe) wires until you find the offender(s). Of course, the new wiring around the new volume pot is to be the most suspect.

G

[greenhorn]

Thanks Guys,
I guess my new baby is ugly
I will get the chopsticks out. (or maybe drumsticks!)

I checked out the lead dress info at geofix. (http://www.geofex.com/Article_Folders/lead_dress/lead_dress_in_tube_amps.htm) This was helpful, but a lot to chew on.

Are all signal wires from pots always shielded? I wish I had an example of this circuit to look at and compare.
Thanks again for the help and I'll post a follow up with higher res pics.

Regards,
Charles

[Geezer]

I guess my new baby is ugly

No, I wasn't commenting on the looks.....the symptoms & circumstances suggest a wire is too close to another signal & oscillating. I always use shielded to & from volume pots, especially for longer runs.

G