Working on a Seeburg JL with metal cased RCA 6L6's. (don't recall seeing those before) While trying to find an intermittent very loud snap, crackle, and pop, I get a bit of a shock off the metal case of the one 6L6. Turns out the plate is shorted to the metal enclosure! The base must be a little small because the tube clips weren't grounding out the B+, although it may have been intermittently and that may have been the noise it was making. Put my meter on it and it was about 395vdc to ground, .1 ohms from pin 3 to the metal case.
Tony