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In Reply to: RE: air tight /acoustic masterpiece 101 posted by kef on July 31, 2017 at 12:03:55
This is an EL34 diagram, the only difference is that the Pin 1 is internally connected to Pin 8 in a KT88.
So what you do is take Pin 4 (G2) and unhook the ultralinear connection from the output transformer. Take that lead and put some heatshrink over the end so it does not contact anything.
Then take a 100 ohm 1 watt resistor and solder it between Pin 3 (plate) and Pin 4 (G2). Check the bias to make sure everything is cool/correct and you are good to go. Most cases the bias will not be adversely affected.
Then enjoy psudo-triode ( I like that connection better if you don't need the power)
Follow Ups:
Ok I feel like something is not quite right. Are the tubes supposed to glow more in triode mode?
Mine do it sounds ok but has me worried.
Thank you!
I feel like someone has had this is triode a lot because the screws for that lead are quite worn. However i looks like no-one has ever put a 100 ohm resistor between 3 and 4, would this hurt the amp if omitted?
Lastly have you done any capcitor /resistor changes, this looks like a great candidate for that.
Thanks
Keith
Don't omit the resistor. It's needed in order to be sure the unbypassed screen doesn't induce parasitic oscillations.
--------------------------
Buy Chinese. Bury freedom.
here is mine
the black electrolytic caps wired across the green 500 ohm resistors....
Are the tops flat? They look like they are swollen (pooched upward).
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
They are ok, but I'm going to replace them with some Elna's I think. But good eye and thanks for looking and taking the time ask.
here is mine
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