WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
My Pop was an electronic engineer, he died recently, and I inherited this from when he was a tv repairmen on the side. It was in his basement, I walked passed it quite a few times thinking it was probably junk, I was wrong!
A lot of TV/Radio repairman used to put used valves back in new valve boxes, they'll need testing to get the best price for them which isn't an easy undertaking for a beginner.