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Initial power up had my voltages in acceptable ranges ... Wife used it weekly for practicing. At one point she said it made some "piercing/shrieking sounds", but then the next time she played it, it "fine for 20 minutes, then the sound cut out and I smelled burning"



One tube socket is charred pretty badly at the terminals between the heater, the screen and anode... But just the one? Could it be a bad tube that shorted?

I'm going to err on the side of me making an error - my connections looked right, I remember biasing correctly for el34 although maybe the bias switch was triggered for some reason ...


In any case any suggestions for cause appreciated! I'm just going to replace the affected components and then start measuring

Oh, that doesn't look good.

I'd replace all the the tube socket and all components associated with it while verifying all your wiring/components.

I would also put in a new set of EL34s.

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You better check the OT as well. Check all the resistors feeding that power tube and see if one failed. Then go back to final checkout and start up in manual.

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Stephen
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