02-22-2026, 10:49 AM
Jeff, NO!! you are NOT wasting your time! Not only are you restoring history, you are gaining troubleshooting skills, so keep at it, and you will get success. Worst case scenario, my usual statement, install a "Radio / Aux Input switch" and jack and you can pipe old time radio through it!
You stated that you moved Cap # 26 negative lead to R24, the important thing is to ensure that you connect the negative lead to the JUNCTION of Resistor #26, Resistor #19 AND the center tap of the transformer HV secondary.
This should not have caused the resistor to burn. Having Cap #26 connected to the chassis would have increased the draw through Resistor #24.
Definitely replace both Resistors 23 and 24 with a minimum of 2 watt resistors.
Next step is to touch the grid cap of the IF tube and determine if there is noise from doing so, especially hum or continued static. If so, that tells us that stage is working. If not, troubleshoot in a similar manner as the Audio stage. Measure Plate, "Grid Plate" voltage on the convertor (1st detector) tube, the 6A7.
If you do not have one, obtain a copy of the RCA Receiving Tube Manual RC13 from 1937. Here is a link to the World Radio History website, a great resource!
https://www.worldradiohistory.com/BOOKSH...13-OCR.pdf.
For some reason, many schematics of this era are published without pin numbers for the tubes. In addition, the RCA Receiving tube has some great descriptions of circuits that these tubes are designed for, and a good description of the "Pentagrid Convertor tube", introduced around 1933 or so.
I will post more later, when I get snowed in.
You stated that you moved Cap # 26 negative lead to R24, the important thing is to ensure that you connect the negative lead to the JUNCTION of Resistor #26, Resistor #19 AND the center tap of the transformer HV secondary.
This should not have caused the resistor to burn. Having Cap #26 connected to the chassis would have increased the draw through Resistor #24.
Definitely replace both Resistors 23 and 24 with a minimum of 2 watt resistors.
Next step is to touch the grid cap of the IF tube and determine if there is noise from doing so, especially hum or continued static. If so, that tells us that stage is working. If not, troubleshoot in a similar manner as the Audio stage. Measure Plate, "Grid Plate" voltage on the convertor (1st detector) tube, the 6A7.
If you do not have one, obtain a copy of the RCA Receiving Tube Manual RC13 from 1937. Here is a link to the World Radio History website, a great resource!
https://www.worldradiohistory.com/BOOKSH...13-OCR.pdf.
For some reason, many schematics of this era are published without pin numbers for the tubes. In addition, the RCA Receiving tube has some great descriptions of circuits that these tubes are designed for, and a good description of the "Pentagrid Convertor tube", introduced around 1933 or so.
I will post more later, when I get snowed in.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis
Best Regards,
MrFixr55




