This is a solid state amp right up to the four 6L6s output stage, and even then there are solid state shenanigans I do not grasp. The complaint is when switched out of standby, there is a loud hum and one pair of 6L6s turns blue. The ones turning blue have recently been replaced, so something is going on with that side. I measure plate -532v, screen = 532v, and grid 15.4v evenly across all four with tubes out.
On the cathodes I get 0.013v on the side that is not turning blue, and 0.003 on the side that is turning blue.
Nothing looks off visually, and the problem stays with the sockets when swapping tubes sides. I really don't know how to procede with this. What is going on at the cathodes? And why is there a big 100R on only one screen of each pair. And most of all why is there 15v on the grids, and no signal? I have never encountered a circuit such as this.
https://www.thetubestore.com/lib/the...-Schematic.pdf
On the cathodes I get 0.013v on the side that is not turning blue, and 0.003 on the side that is turning blue.
Nothing looks off visually, and the problem stays with the sockets when swapping tubes sides. I really don't know how to procede with this. What is going on at the cathodes? And why is there a big 100R on only one screen of each pair. And most of all why is there 15v on the grids, and no signal? I have never encountered a circuit such as this.
https://www.thetubestore.com/lib/the...-Schematic.pdf
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