Problems, Lots of hum. Can’t find a schematic on this one. It uses 2 BEU7’s 4 12au7’s and 2 7191’s for the output. I can remove every tube except the outputs and still hum. Checked a lot of voltages and everything seems ok. Still hum. Replaced the 20uF filter caps. Still hum. Tried new outputs. Still hum. Any ideas? There’s not that much to it.

This is a tricky one... Are the output tubes matched? Maybe you have a ground loop... Maybe a ground connection has a cold solder joint...

Maybe somewhere a wire is picking put AC from another wire? More a few wires around...

good luck