6080/6AS7 cuts out after about 3 minutes [solved]

[Twodawgzz]

If I move it around a bit in its socket it sometimes comes back on for another 3 minutes or so.  Completed the build about a week ago, and nothing seemed to be amiss.  All resistances and voltages checked out, and the sound through headphones is great.

Any suggestions or words of wisdom?

[Doc B.]

You have a bad heater pin connection. Resolder the wires connected to the heater pins, and try cleaning the tube pins with a scotchbrite pad.

[Twodawgzz]

All right.  Will do.  Thanks.

[Twodawgzz]

You have a bad heater pin connection. Resolder the wires connected to the heater pins, and try cleaning the tube pins with a scotchbrite pad.

Problem not solved.

I unsoldered and carefully resoldered all heater pin connections and cleaned the tube pins.

When I turned the amp on, it took a good couple of minutes before the 6080/6AS7 glowed.  Listening to music through the amp, it then worked fine for about 7 minutes, and the tube then shut down (but not the 12AU7).

So what should I check next?

[Doc B.]

The next thing to do is check to see if there is actually voltage present at the tube pins when the tube is not glowing. That will determine if the tube is at fault or if the voltage is not getting to the tube socket. If, when the tube stops glowing, you can get it to glow again by rocking the tube in the socket a little, it's the socket or wiring and not the tube.

[Grainger49]

You might want to try snugging up the heater socket.  Bending it a little tighter.

Can't hurt, might help.

[Twodawgzz]

Checked all and redid some solder joints.  6AS7 still not heating up.  Checked it with my Eico 667 Tube Tester and get absolutely no readings.  At the same time, it appears I have another problem.  While all voltages, etc., checked out immediately after the build, now I'm getting no voltage readings from Terminals 7, 9, B3, and B6.

[Doc B.]

Is the 6080 not glowing in the tube tester?

[Twodawgzz]

Nope.

[Twodawgzz]

Is the 6080 not glowing in the tube tester?

Not glowing.

So Doc... what happens next?  Do you send me a replacement tube?  Does my comment about zero voltages make sense if the 6080 is dead... or is something else also happening?  I am your customer Walt Weiskopf, by the way, who ordered the Crack on Nov. 30, 2013, I believe.

[2wo]

Just to be sure, you can check the resistance of the heater, pins 7 & 8. should be pretty low...John 

[Twodawgzz]

Problem solved.  Output tube was bad.  With replacement 6080 the amp is now working fine and sounds unbelievably great!

Thanks Doc B!