Ekco UL84 Voltage Issue

[Diabolical Artificer]

Valves are pretty hardy & in the days when they made UL84's and they cost 3s it didn't matter if the valve was running hard, as there is now a finite supply of UL84's and they can fetch a tenner it may be worth bunging a grid dropper or stopper on g2. Datasheet says Va 170, Ia 70mA, Ig2 5mA, so if we want to drop 5v ish you'd need a 1k between HT and g2, that's if you can get to the base etc to do the work. To do the job properly you'd also put a 100r approx grid stopper after the 1k with a 0.1u - 10u cap de-coupling the 1k to ground, that might be a bit overkill for this case though.

A 1/2w 1k will be sufficiant, if you wanted to drop a tad more a 1k5 or 2k2 should do the job.

Andy.