09-26-2023, 09:18 PM
Hi Pholks,
I am working on a Philco 20. The unit is all original and works, but the Customer is looking for reliability. I have one myself, but I think that it was worked over in the late 1930s or early 40s with replacement caps external to the Bakelite blocks (Whoever repaired this at least did isolate the bakelite caps). The resistors were all the 2" long brown jobs with modern bands using the modern color code, so I don't think that those were original. So for mine, I just replaced all the caps that were replaced lo those years ago. I had to rewind the RF trans between the 2nd RF and Detector due to an open primary. Mine was missing the speaker (and cabinet) so mine plays through a modern 8" speaker in a rather beat up cabinet that I got off ePay. The Customer has a rather nice cabinet of the later style (The 2 columns on the lower front adds a lot to the cabinet IMHO), and he DOES have the pie plate speaker. I am not sure which style spider his has.
Are the glass cartridge style resistors (They seem to have ceramic-like bodies and metal end caps) original equipment in the Philco 20 or should they the ones with wound wire capping the ends? Which of these two styles are referred to as dog bones? (I think it is the type with the wirewound ends, but I defer to you experts.) If replaced with modern resistors, what wattage should be used for the cathode resistor for the detector, the 250 Ohm resistor that is part of Bakelite Block #8, the 1st audio's grid resistor and the dropping resistors for the detector plate voltage? Are half watters sufficient? (The Customer has no interest in the expense of stuffing the blocks or having original resistors but is looking for reliability). The RF Coil Plate windings are good, but original, so I will likely rewind them to prevent the failure that is common to Philco coils of this vintage.
Tubes were all replaced at various times and are of the "ST" variety. The 24As are Philco brand but are marked "For replacement use only".
How reliable or unreliable is the wirewound voltage divider and the main filter cap? I am tempted to replace both, as the customer intends to use this radio.
I would have done John Grady's and Ron R's cap coupled mod to the interstage audio transformer but the primary is blown and someone already "bridged" the interstage transformer.
Thanks for the help!
I am working on a Philco 20. The unit is all original and works, but the Customer is looking for reliability. I have one myself, but I think that it was worked over in the late 1930s or early 40s with replacement caps external to the Bakelite blocks (Whoever repaired this at least did isolate the bakelite caps). The resistors were all the 2" long brown jobs with modern bands using the modern color code, so I don't think that those were original. So for mine, I just replaced all the caps that were replaced lo those years ago. I had to rewind the RF trans between the 2nd RF and Detector due to an open primary. Mine was missing the speaker (and cabinet) so mine plays through a modern 8" speaker in a rather beat up cabinet that I got off ePay. The Customer has a rather nice cabinet of the later style (The 2 columns on the lower front adds a lot to the cabinet IMHO), and he DOES have the pie plate speaker. I am not sure which style spider his has.
Are the glass cartridge style resistors (They seem to have ceramic-like bodies and metal end caps) original equipment in the Philco 20 or should they the ones with wound wire capping the ends? Which of these two styles are referred to as dog bones? (I think it is the type with the wirewound ends, but I defer to you experts.) If replaced with modern resistors, what wattage should be used for the cathode resistor for the detector, the 250 Ohm resistor that is part of Bakelite Block #8, the 1st audio's grid resistor and the dropping resistors for the detector plate voltage? Are half watters sufficient? (The Customer has no interest in the expense of stuffing the blocks or having original resistors but is looking for reliability). The RF Coil Plate windings are good, but original, so I will likely rewind them to prevent the failure that is common to Philco coils of this vintage.
Tubes were all replaced at various times and are of the "ST" variety. The 24As are Philco brand but are marked "For replacement use only".
How reliable or unreliable is the wirewound voltage divider and the main filter cap? I am tempted to replace both, as the customer intends to use this radio.
I would have done John Grady's and Ron R's cap coupled mod to the interstage audio transformer but the primary is blown and someone already "bridged" the interstage transformer.
Thanks for the help!
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards,
MrFixr55
