Does anyone have access to Stancor audio transformer specs? An A-3878 has been subbed inside my Philco 39-7. Doesn't sound too, too bad, just a little pinched (no lows). I don't know if it's a good enough match for the 41 output tube. Thanks.

:Does anyone have access to Stancor audio transformer specs? An A-3878 has been subbed inside my Philco 39-7. Doesn't sound too, too bad, just a little pinched (no lows). I don't know if it's a good enough match for the 41 output tube. Thanks.
Jim A-3878 is a Class A 7000 ohm primary and 4 ohm secondary transformer. It's rated at 30ma dc primary and 5 watts. My Stancor catalog says this transformer has a 10% inverse feedback winding also. Some of the tubes recomended are : 6K6 6F6 42 2A5

Hi

Just for information 41 is the same as 6K6 electrically. If you are missing lows try increasing your coupling cap value going to pin #4 on a 41 tube.

Norm

::Does anyone have access to Stancor audio transformer specs? An A-3878 has been subbed inside my Philco 39-7. Doesn't sound too, too bad, just a little pinched (no lows). I don't know if it's a good enough match for the 41 output tube. Thanks.
:Jim A-3878 is a Class A 7000 ohm primary and 4 ohm secondary transformer. It's rated at 30ma dc primary and 5 watts. My Stancor catalog says this transformer has a 10% inverse feedback winding also. Some of the tubes recomended are : 6K6 6F6 42 2A5

:Does anyone have access to Stancor audio transformer specs? An A-3878 has been subbed inside my Philco 39-7. Doesn't sound too, too bad, just a little pinched (no lows). I don't know if it's a good enough match for the 41 output tube. Thanks. Forgot to mention the 39-7 shows a .006 mfd cap across the primary and the original Philco transformer primary resistance was 850 ohms. The A-3878 has an impedance of 7000 ohms.

Thanks, guys. Did a little more fooling around since it appears the Stancor transformer is probably not the problem. All the paper caps have been replaced, but I notice that the .006 "quality cap" on the primary does nothing. I start to notice damping of the highs with values of .022uf and up. Upping the coupling cap to .05 does nothing. Bias about -8.4v. Plate and screen volts about +15v high. The more I listen to this radio, the more it just sounds "dirty". The kind of audio that most people would not remark about, but that would quickly cause listener fatigue. And, exactly the same audio I have found in one or two other Philco tabletops. I think the next step is to go back one stage and see what's up there. If anyone has other thoughts, I would be glad to hear 'em. Thanks again.
Jim