12-23-2013, 09:05 AM
No, I am not saying that I am not replacing all the paper capacitors. I am saying that I discovered this in the process of replacing them. This one would have been a deal breaker if I had applied power. Checking for shorts to ground in the B+ circuitry is always a good thing to do after or during repair and this was part of that process. The other thing I am finding as I continue replacing capacitors is that the resistors have changed in value anywhere from 19% to 57%! That was in the phase splitter circuit alone! There is no telling how many more are off value at this point. It appears that most all of the capacitors except for mica types will wind up being replaced. Many of the paper capacitors have already been replaced in the past, but I do not trust the replacements. This example goes to show just how bad these old paper capacitors can get.
I restored negative feedback to the audio circuits by adding a 5 ohm and 68 ohm resistor string at the output transformer secondary and running a new wire back to the low end of the volume control and tone control center lug like originally done by Philco. I did not have a 4.7 ohm resistor like Philco used in their late 1940 series of radios, but had lots of 10 ohm resistors on hand. I bridged two in parallel to create a 5 ohm resistor. I removed the switch and phonograph jack from the radio as it turned out, the switch was very intermittent and because of the way it was constructed it could not be cleaned internally. I might still add a phonograph input, but it will be an RCA type jack instead of the1/4" phone jack type that was used here.
Cheers!
Joe
I restored negative feedback to the audio circuits by adding a 5 ohm and 68 ohm resistor string at the output transformer secondary and running a new wire back to the low end of the volume control and tone control center lug like originally done by Philco. I did not have a 4.7 ohm resistor like Philco used in their late 1940 series of radios, but had lots of 10 ohm resistors on hand. I bridged two in parallel to create a 5 ohm resistor. I removed the switch and phonograph jack from the radio as it turned out, the switch was very intermittent and because of the way it was constructed it could not be cleaned internally. I might still add a phonograph input, but it will be an RCA type jack instead of the1/4" phone jack type that was used here.
Cheers!
Joe