[Patrick]

I recently finished a 40-190 with the same 7J7 to 6J8 change.  The schematic shows only the 7J7, but in mine, the wiring and components to the 6J8 were the same as the shown on the schematic, taking into account the connection to the 6J8 grid cap wire instead of a grid pin on the base.

Mine has a 150 ohm resistor from pin 6 of the 6J8 to ground. Maybe that's why the 4.7K (R29) is getting hot. Even with the 6J8 pulled, I get 140V before R29, and less than 5V after it (right on the tube socket pin).