New VTA-70 Build - Right Channel Cutting Out After 10-15 Minutes - fixed !

The title pretty much sums it up, and it's frustrating the heck out of me.  This is a newly completed VTA ST-70 build with all new tubes, new Authenticap, added the recitifier diodes, and toggle switches for the triode/pentode switch.  I turn the amp on, play some music for a while (it sounds wonderful BTW!), after 10 minutes or so I loose the right channel of the amp.  The bias is steady at ~ 0.4 vdc, I've swapped the left and right interconnects, swapped the speaker wires, swapped the output tubes, and even swapped the input on the Lazarus Cascade Basic preamp, yet the problem continues and points to the right channel of the amp.  No hiss comes from the speakers when this happens.  Letting it cool off doesn't typically solved it.  If I disconnect everything then reconnect, it usually works normally for a few minutes then cuts out.  I've looked over all the wiring and pcb, and can't seem to find any obvious problems.  What else can I do to trace the cause?  OPT?

One possible variable I hadn't swapped is the drive tubes, so I switched those up and the amp started working again.  However within 5-10 minutes the right channel went out again as it's been doing.  Wiggling the center drive tube yielded output from the right channel again.  As I wiggled it some more, I could hear the right channel going in and out, so I added some pressure and made sure it was really well seated.  Maybe the center tube wasn't quite seated fully, or is at least near the root cause.  The problem still persists, but wiggling the center drive tube seems to consistently fix it temporarily.  I'll have to take another look at all the solder connections on that socket.

Maybe check your solder connections.

Sounds logical guys. Will do. Thanks.

Well I opened up the amp resoldered the connections around the middle and right driver tube socket.  That seems to have done the trick!  Thanks again guys!

Edit: It's been another 48 hours since I posted about the fixresoldering the sockets, and have logged several hours of playing time on the amp since then. All is well, so I'm confident it's working as it should! (as you probably expected!)