02-19-2026, 09:29 AM
Hi DM Blackburn,
Yes, it is possible for that cap block to cause problems. The "Block" contains several "bypass" caps that is meant to prevent the undesired coupling and feedback between stages through the common power supply.
Morzh is correct. Unfortunately, these radios are very old, and the materials used to construct these capacitors deteriorate, sealed in tar or not. Newer caps using mylar or other plastics for dielectric are more stable and durable than paper and oil, etc.
It was very insightful of you to attempt to determine "outside foil" which is no longer marked on so many of these newer caps, even those from "reputable" manufacturers. However, some or many of these caps do not have an "outside foil" effect.
Do go about servicing the Bakelite blocks ASAP, as failure of these caps may actually cause damage. One specific example is the shorting to the bypass cap between plate and cathode r plate and ground of the output tube. This can burn out an output transformer. Shorting of the coupling cap between the plate of the 1st audio tube and the grid of the audio output can cause excessive current draw, "Red Plating" and destruction of the output tube, burnout of the output transformer, rectifier, power transformer, etc. Replacing these caps increases the safety of operating the radio.
When I was a kid, a filament to plate short of a 5Y3 took out a power transformer of an old Philco (I don't remember the model, it was a street find, but as likely late pre-war or early post-war) filled the house with smoke and there were flames when I discovered this. My Mom TOTALLY FREAKED OUT and demanded that I put the set to the curb immediately. Dad, who had the last word in our house (Yes Dear, No Dear, I'm sorry, Dear, etc.) would not overrule Mom's decree, therefore, I was not even able to scavenge tubes, speaker, etc or perform a "post-mortem examination". I don't know if the failure was a spontaneous failure of the transformer, a spontaneous failure of the tube (cathode to plate short), failure of a cap shorting the B+, etc.
2 Mods that I always try to do on transformer powered sets is to place silicon rectifiers in series with the rectifier, between the secondary and the rectifier plates, and to fuse the power input to the radio. This will minimize the effect of a direct short across the secondary of the power transformer if the tube shorts.
Yes, it is possible for that cap block to cause problems. The "Block" contains several "bypass" caps that is meant to prevent the undesired coupling and feedback between stages through the common power supply.
Morzh is correct. Unfortunately, these radios are very old, and the materials used to construct these capacitors deteriorate, sealed in tar or not. Newer caps using mylar or other plastics for dielectric are more stable and durable than paper and oil, etc.
It was very insightful of you to attempt to determine "outside foil" which is no longer marked on so many of these newer caps, even those from "reputable" manufacturers. However, some or many of these caps do not have an "outside foil" effect.
Do go about servicing the Bakelite blocks ASAP, as failure of these caps may actually cause damage. One specific example is the shorting to the bypass cap between plate and cathode r plate and ground of the output tube. This can burn out an output transformer. Shorting of the coupling cap between the plate of the 1st audio tube and the grid of the audio output can cause excessive current draw, "Red Plating" and destruction of the output tube, burnout of the output transformer, rectifier, power transformer, etc. Replacing these caps increases the safety of operating the radio.
When I was a kid, a filament to plate short of a 5Y3 took out a power transformer of an old Philco (I don't remember the model, it was a street find, but as likely late pre-war or early post-war) filled the house with smoke and there were flames when I discovered this. My Mom TOTALLY FREAKED OUT and demanded that I put the set to the curb immediately. Dad, who had the last word in our house (Yes Dear, No Dear, I'm sorry, Dear, etc.) would not overrule Mom's decree, therefore, I was not even able to scavenge tubes, speaker, etc or perform a "post-mortem examination". I don't know if the failure was a spontaneous failure of the transformer, a spontaneous failure of the tube (cathode to plate short), failure of a cap shorting the B+, etc.
2 Mods that I always try to do on transformer powered sets is to place silicon rectifiers in series with the rectifier, between the secondary and the rectifier plates, and to fuse the power input to the radio. This will minimize the effect of a direct short across the secondary of the power transformer if the tube shorts.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis
Best Regards,
MrFixr55
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