Ampeg B22X with multiple problems

[nosaj]

I am pretty sure you really can't measure the grids unless you use a VTVM something about the loading impedance. Good deal you got it figured out. Maybe the can lug has a higher resistance to ground giving a positive feedback?
OTOH we just got power back today.

nosaj

[Randall]

I wasn't measuring grids. Pin 8 is a plate feeding the bottom output tube, pin 1 is the plate feeding the top output tube. I can probe pin 1 with no consequence, but pin 8 raises hell.