Well it was a bit of a process, but not bad really. What I think happened was a bad solder joint on the power supply ground during my re-build led to that runaway bias. After a couple days trouble shooting I discovered the bad joint and fixed it, what I didn't know is the runaway bias damaged the rectifier tube. The tube apparently was a bit intermittent, coming up normally for about four minutes, then dropping off so that it takes full pot to get about 1.4 volts. I think that day that I played the amps for 30-40 minutes, the rectifier kicked in a was running full bias for 10-15 minutes, that's why the amp got so hot.
Yesterday I put an old, still good Sylvania GZ34 in the amp and it biased perfectly and held steady for 30 minutes. Then I hooked both amps up to my system and played music, wow is all I can say. These are really nice amps, lots of good clean power and now they are running nice and cool. Based on some internet advise about setting the bias a little lower due to today's higher line voltage (mine is 123 volts), I set my bias at 1.50 rather than 1.56. Anyway, thank you for your patience and good ideas while I struggled with this over the last week.
John
Yesterday I put an old, still good Sylvania GZ34 in the amp and it biased perfectly and held steady for 30 minutes. Then I hooked both amps up to my system and played music, wow is all I can say. These are really nice amps, lots of good clean power and now they are running nice and cool. Based on some internet advise about setting the bias a little lower due to today's higher line voltage (mine is 123 volts), I set my bias at 1.50 rather than 1.56. Anyway, thank you for your patience and good ideas while I struggled with this over the last week.
John