variable 3rd stage Rk?

[mhuss]

The issue with potentiometers as plate loads is the *voltage*, not the wattage. There's precious little insulation and clearance inside to be keep hundreds of volts away from the cover (and metal shaft!) Even if you don't electrocute yourself, you could have quite a fireworks display as the HV power supply gets grounded via the arcing pot.

--mark h

[PeteRH]

The issue with potentiometers as plate loads is the *voltage*, not the wattage. There's precious little insulation and clearance inside to be keep hundreds of volts away from the cover (and metal shaft!) Even if you don't electrocute yourself, you could have quite a fireworks display as the HV power supply gets grounded via the arcing pot. --mark h

Thanks for the correction Mark.

It is worth bumping to the top again. Don't use pots for plate resistors.

Cheers
PeteRH