Fender twin reverb

[Big chief]

Silver face twin with master volume  squeal reverb when pot is set above 7
Tried 3 different tubes retintion tube sockets cleaned all connections V3 is microphonic to the touch no matter what tube I use if I hold my hand on tip of guitar cable and touch V3
The squeal appears to go away any help would be helpful. Thanks

[Lectroid]

When you touch the cable, are you touching the cable itself or the plug?   A plug's metal cover is connected to ground and it's possible that your touch is creating a new ground path for the circuit that is currently missing.  I would look at the Reverb pot ground connection, and any other grounded components in that circuit path.  Chances are one of them's loose or got a cold solder joint.

[Latole]

Never, never touch a tube and other part of the amp in same time.

[Big chief]

Bad ground at reverb pot thanks for your help