Grid coupler change?

[Mike Watterson]

Hi.
Also increasing the cathode resistor value helps. You need to measure the cathode voltage and subtract the grid volts, this with tell you the grid volts WRT cathode that should be a negative value in the order of 5 to 7v, also if you measure the cathode volts and calculate the current by ohms law you'll know if the valve is over driven.

PS I've seen boards far worse than that and the G1 volts are not excessive.

Also why not lift the track to the grid away from the PCB and just use insulated wire to make the connection away from the overheated section

Better than my suggestion.

And drill out the PCB at the grid pin of socket so grid is only wired to cap and resistor via insulated wire.