tube amplifier problem, pls help me

[poohjangnim]

I built a 20 watts amplifier with 12ax(2pcs) & 6L6wgc(1pcs) tube.The First time I switch my amplifier in a day, there is no problem, sounds great but when I turn it off, after few minutes I turn it On again, NO Sound will come out. while I am debugging it I found out that it will start to make a sound when I tap the PIN 2 of the second tube(12ax) into the ground for 20seconds.If I don't tapped it to the ground even in hours it will not make a sound.

Please help me to solve this problem. thanks in advance.......

[PerroGrande]

You probably have a bad solder connection or a bad tube socket.  It is possible that the valve itself is bad, but I'd explore the other two options first, as they are far more likely to be the cause.

[poohjangnim]

thanks, I already changed the tube many times but still the problem  is the same. I will try to solder all today.thanks again.

[Ardric]

Maybe you don't have a DC path from the grid to ground through a volume control or something, so the bias is running away.

Try adding a 1M resistor between that pin 2 and ground.

[birt]

and before you resolder everything poke around with a chop stick. you might find the bad connection a lot easier without all the extra work.

[poohjangnim]

thanks for replying. I already solder everything but still problem. I will add later a 2M resistor later.thanks guys......

[wlrs]

Check the fuse

[poohjangnim]

ARDRIC thank you, i got the idea from your suggestion.your correct that i don't have a dc path but not on the pin two which is the pre amp.I add the 1M resistor on my power tube which has no dc path.

Your great ARDRIC........thanks a lot...