[ghjkl67]

Just to clarify, I think you mean 2A4G, not 2A3G.

I looked at the wires going to the filament transformer. It appears to be a factory soldering job. I'm going to leave it there until the new 2A4G thyratron comes in that I ordered. The one that's in there now is already NOS, but it still could be defective.

I already tried disconnecting the thyratron grid. Wouldn't that isolate it? I don't see the need to remove the 6J7G for testing, but I'll do it anyway. Again, when I disconnected the thyratron grid from circuit and left it hanging, it remained activated. Sometimes, poking at the tube socket terminals would cause the tube to activate after cold start. I assume it should remain off the entire time the grid is disconnected. Is that correct?