I think I might just do what Sirbuh did... if Fender won't just replace it after this repair i'll try and sell it as a like new amp for 700 and just go get a 6505 plus.... this 5150 has such a great clean tone though... sucks! I really loved the sound and features of this amp. Why are they so popular if they break down? I really think I got a lemon. But it sounds like i'm not the only one.
Something to consider , I did have the 6L6 combo (earlier run) and it didn't have these issues.
However the shop (final, non fender shop) I took in the el34 mentioned they had an up tic in issues.
It is possible that the earlier pre el34 years are more stable.