10-20-2023, 08:27 AM
For testing purposes what you could do is use the opt as is. Since the stage uses triode sections of the opt tube there is no issues with damaging the screen grid thru over dissipation. There will be a slight drop in output about 15% but 19 is a pretty stout tube.
This holds true for triode connected tetrodes or pentodes. Like the Philco Super Class A output stage (P/P 42's w/the screen grid connected the plate). Bob and I did it on a 116B w/a 1/2 open opt.
What you don't want to do is is operate a set w/1/2 an opt and tetrodes or pentodes that the screen grid are connect back to hv line. In this configuration there is no plate voltage on the plate. So, the screen acts as the plate would but it can't dissipate the current that the plate can. In some cases, the screen will light up and burn up and tube's gain drops to 0. I think I hear Chopin playing in the background. (No Copyright Music) Funeral March (by Chopin) by Chopin - YouTube
File this under cheap tricks. [Image: https://philcoradio.com/phorum/images/sm...on_lol.gif]
This holds true for triode connected tetrodes or pentodes. Like the Philco Super Class A output stage (P/P 42's w/the screen grid connected the plate). Bob and I did it on a 116B w/a 1/2 open opt.
What you don't want to do is is operate a set w/1/2 an opt and tetrodes or pentodes that the screen grid are connect back to hv line. In this configuration there is no plate voltage on the plate. So, the screen acts as the plate would but it can't dissipate the current that the plate can. In some cases, the screen will light up and burn up and tube's gain drops to 0. I think I hear Chopin playing in the background. (No Copyright Music) Funeral March (by Chopin) by Chopin - YouTube
File this under cheap tricks. [Image: https://philcoradio.com/phorum/images/sm...on_lol.gif]
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
