Ampeg SVT Trio intermittently dropping out.

[bakerlite]

Hey folks -
Bit of a headscratcher
I have a SVT Classic thats giving some problems - I beleive it s a physical connection/solder joint somewhere but cannot for the life of me track it down.
Basicaly amp runs fine sounds good bias lights perfect (green at idle, switch to red when playing).
BUT sometimes a trio drops out. It can be like that from switch on or maybe during playing it might go.
The fullness of sound dissappears and the bias lights on one side dont work like normal when this happens.
I can temporarily fix this by applying the gentlest wiggle/pressure to the board at the back where the 12au7's and ax7 is and the slave out jack. any further up than the slave out jack and the wiggle doesnt effect the problem.
Thing is there isnt a sure way to make the problem happen or cause the problem to happen -
right now wiggling any of those 3 tubes or the left bias pot causes it to come back to full power or drop out depending whether i push/wiggle up or down!
Any Ideas? or methods you would suggest to hunt it down?

[bob p]

Sounds like an intermittent connection.
I'd check all of the ribbon connectors to assure they are all tight, and I'd replace them if needed.
I'd also remove the boards from the chassis and go over all of the solder joints/connections.
I'd also inspect the traces on the board that you've been wiggling, sockets, etc.

[Jazz P Bass]

Resolder the board.
Retension the socket pins.

[Enzo]

12AU7 losing socket contact or failing.