Quote:
Originally Posted by init4fun
 Hi Tubeguy ,
Any time I've encountered runaway cathode current , it has always been found to be either the grid circuit capacitors failing and driving the grid positive or a bad tube as old coot suggested . I've seen both gassy and tubes that have developed "secondary grid emission" do the runaway cathode current thing , but mostly find it in the capacitors slowly going partially shorted . |
I was going with a gassy tube since he said it starts out normal at 200ma then climbs gradually. Whereas a leaky grid coupling cap woulda put the current high immediately.
But that cap should
always be replaced as a matter of course anyway. Same goes for the grid coupling cap feeding any power stage (audio output, vert. output).