Hello,im steve, have’many’boogies, had that in one of my mkv-35, only a bit noisier.
did all tubes 1x1, was i think the v3 or 4 cant remember. Just do the process of elimination.am sure youll find its a noisy 12ax7,think you have 4 oer 5in thier. I have 2-50s 7 a 100 fillmore, LOVE EM