• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Max screen grid voltages in datasheets


2014-04-22 3:18 pm
I'm running 6L6GC triode connected. The 6L6GC datasheet says the maximum screen grid voltage is 450V. Are those maximum ratings for DC-condition or for AC-condition? In triode connection the screen grid voltage could easily have higher peaks than this 450V.
Any thoughts about safely operating the 814 transmitter tube triode connected?

How do you avoid arcing at the base/socket, when g2 is at the same potential as plate? The plate was brought out to a top cap, for very good reason. Compare the ratings of the TT21, with its plate cap, to those of the KT88. Internally, the 2 types are identical.
A few things:
1. that circuit runs into class 2, where grid current takes up the slack from a low screen/plate voltage.
2. Triode mode doesn't dissipate too much screen current/power anyway, as mentioned.
3. The voltage rating isn't just because of screen dissipation, or arcing, though those are important factors. Typical screen ratings drop off hyperbolically above the nominal rating (e.g., See RC-26, curve page 98).

For pulsed and current limited operation, the ratings are usually higher: compare ratings as vertical or horizontal deflection amplifier against typical linear amplifier ratings. Of course, that doesn't mean anything if you want to use it in linear amplifier service in the first place...