Hi Guys,
I haven't been around for a while but a project fell in my lap and has me stumped. I'm working on a friend's 5E6-A 4X10. It is bone stock except for fairly new filter caps. The RCA 6L6s are pulling 66 ma each. I subbed in a new bias cap and subbed in a UF4007 in place of the selenium rectifier (which still works fine). I switched tube positions and subbed in a pair of TADs to be sure. They only pulled 61 ma but you get the idea. I'm using the shunt method. Screens are 410 and B+ is 420.
On very low gain I ran a 1k sine wave into the jack and it looked fine all the way through the amp -- so I'm guessing there aren't any hidden parasitics lurking. The PI caps test good (old Astrons). The crux of the issue is that the bias tap puts out 46 volts -- right on the schematic. At the grids it is -41 volts which is a pretty efficient exchange. I'm not losing bias volts anywhere. I did put another 20k resistance on the bleed resistor to see if it would make a difference and it did raise the bias voltage a volt and the rail by 5 -- so it is open to persuasion.
So, two questions: any ideas and does the shunt method work when the B+ goes to both the center tap and the screens? Thanks for your help, Skip
I haven't been around for a while but a project fell in my lap and has me stumped. I'm working on a friend's 5E6-A 4X10. It is bone stock except for fairly new filter caps. The RCA 6L6s are pulling 66 ma each. I subbed in a new bias cap and subbed in a UF4007 in place of the selenium rectifier (which still works fine). I switched tube positions and subbed in a pair of TADs to be sure. They only pulled 61 ma but you get the idea. I'm using the shunt method. Screens are 410 and B+ is 420.
On very low gain I ran a 1k sine wave into the jack and it looked fine all the way through the amp -- so I'm guessing there aren't any hidden parasitics lurking. The PI caps test good (old Astrons). The crux of the issue is that the bias tap puts out 46 volts -- right on the schematic. At the grids it is -41 volts which is a pretty efficient exchange. I'm not losing bias volts anywhere. I did put another 20k resistance on the bleed resistor to see if it would make a difference and it did raise the bias voltage a volt and the rail by 5 -- so it is open to persuasion.
So, two questions: any ideas and does the shunt method work when the B+ goes to both the center tap and the screens? Thanks for your help, Skip
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