03-30-2014, 07:56 PM
Hay BAD. I think it is a reflection or the color settings on your monitor.
Those should be 7189As. The tube I would vote for being the most over driven of all of the (regular) audio OP tubes. It is a 6BQ5 run at about 425V on the plate. So If it is glowing , I understand.
Since only one of the original OP tubes was in place I had to go with the Ruski version. I did add a few watts of primary resistance.
So I think the plate voltage was about 385V. I was as careful about the bias as I could be since it is developed by using the filaments of the 12AX7s as a series string resistor. As I recall it ends up averaging about 8 or 9 volts on each 12AX7. Supposed to keep them quiet, but if anything goes wrong you have red plates and burnt out filaments. I think they should have spent a few more $ on the power supply instead. Anyway I also added the forced air instead of carving a hole in the nice cabinet I built.
He has had it for a year and has not reported any fires.
Those should be 7189As. The tube I would vote for being the most over driven of all of the (regular) audio OP tubes. It is a 6BQ5 run at about 425V on the plate. So If it is glowing , I understand.
Since only one of the original OP tubes was in place I had to go with the Ruski version. I did add a few watts of primary resistance.
So I think the plate voltage was about 385V. I was as careful about the bias as I could be since it is developed by using the filaments of the 12AX7s as a series string resistor. As I recall it ends up averaging about 8 or 9 volts on each 12AX7. Supposed to keep them quiet, but if anything goes wrong you have red plates and burnt out filaments. I think they should have spent a few more $ on the power supply instead. Anyway I also added the forced air instead of carving a hole in the nice cabinet I built.
He has had it for a year and has not reported any fires.
