Heater woes. Gimme some ideas please.

[Frankie Sixxxgun]

Okay, the amp in question is my Metroamp 50 watt Plexi and the behavior is as follows. Occasionally I'll lose heat to V1 and V2, the rest of the tubes stay hot. I've cracked open the chassis, checked my heater runs, nothing is visibly grounding out that I can see. I've checked for loose strands or anything that could be the culprit... nada. Now, if I jiggle the tube in V2 (old Mullard b-code), sometimes it'll come back to life. It actually did this to me twice on stage Saturday, but I knew better and had my back panel off, so I was able to give a technical tap back to life mid set.

Now, what puzzles me is that the heaters are in parallel, so wouldn't a ground out take out all the tubes since a shunt to ground should have way less resistance than a heater filament? What could cause just V1 and V2 to die out? What diagnostic steps should I take here?

Obviously tonight I'm gonna yoink all the tubes and put 'em in one by one from V1 forward to see if they heat. I'll also try another tube in V2 just in case it's internally shorting. Could the tube socket itself have a small crack or something I can't see that'll allow the heater voltage to shunt out? Still... wouldn't that take out all the heat?

Oh, I can also hear the PT humming slightly, like it's taxed. Not sure if that's normal with these Heyboer trannys.

[Roe]

reflow soldier joints

[Frankie Sixxxgun]

reflow soldier joints

At V2 and V1?

Nevermind, reflowing at V3 seems like the most appropriate, huh? I'll check the connections there.