when a tube goes bad.....

[gary sanders]

I had one start pulling almost double on the plate volts.Started around 178 and then put another in and it was pulling 310!Discarded that tube and amp s fine and V is good.Just wondering what causes a tube to suck in some voltage like that when it craps out

[martin manning]

I assume you are talking about a resistance-loaded (pre-amp) tube here? The plate voltage will increase as the curent flow decreases. If the tube ceases to conduct any current at all, the plate voltage will be equal to the supply voltage.

[gary sanders]

That makes sense I was just wondering how it worked,well,I guess cause it doesnt "work....".Now I get to crack it open and look at its guts.

[Structo]

Gary be careful if you open that tube.
They used to use (and probably still do) some nasty chemicals in tube manufacturing.
Including different gasses.

[gary sanders]

Thanks for the warning! I didnt know that either.I will get my ex wife to do it for me