08-21-2026, 09:45 AM
Hi Daniel,
Thanks for the pictures. It appears that the person tried to do a good job and tried to make a European version of a common American 5 tube circuit that was popular from about 1941 to the end of the vacuum tube era in the USA. The "All American 5" circuit used a "pentagrid" (heptode) converter, a "remote cutoff" pentode for the IF (intermediate frequency) stage, a combination diode / triode tube for the detector and first AF Amp and a power pentode for the audio power output amp. The DC for the set was provided by a rectifier. The original Philco 54C was an early version of this circuit. It seems that the person rebuilding this set also replaced the IF transformers and all capacitors and resistors. Nothing other than the tuning capacitor, speaker and the chassis itself is original.
The filaments (heaters) for these tubes are wired up in series. if the total operating voltages of these heaters in series did not add up to power line voltage, then resistance had to be added to compensate for this. In the US, the popular tubes were a 12SA7 (converter), 12SK7 (IF), 12SQ7 (Detector / 1st AF) 50L6 (Output) and 35Z5 (Rectifier). These heater voltages added up to approximately 120 Volts. The original 54C had heater voltages that added up only to 68 volts at 300 mA so sufficient resistance had to be added to make up the mains voltage.
It seems that the only original parts that remain in this set are the chassis, speaker and the tuning capacitor.
My recommendation is to make a note of the tube types used in the modification to your set. Feel free to list the numbers on the tubes here. Thee appear to be European 7 pin or 9 pin miniature tubes. If they have the same functions as listed above, try to trace out the current diagram based on the tube diagrams for the tubes used. The circuit may be legitimate. Do change out the electrolytic capacitors. Everything else should be OK, but you have to determine, based on the total heater voltages and any resistors in series with the heaters (they may have used a motor capacitor instead of a resistor) to determine the voltage that the original rebuilder designed this radio to operate from.
THE ONE BIG ISSUE HERE IS SAFETY!!!!
Radios of this type have their chassis connected to one side of the power line. Worse, that usually happens through the power switch making the radio to be dangerous no matter how the plug is inserted. I assume that in Europe, one side of the power line is at "Earth" ("Ground") potential If your mains voltage is in the order of 220 volts, this makes it even more dangerous. The original Model 54C had an interlock to completely disconnect power when the back was removed.
Here is a link to a very good article on this issue:
https://antiqueradio.org/safety.htm
If you can't get to this document or need it translated to Espanol, let me know.
Good luck and God Bless!
Thanks for the pictures. It appears that the person tried to do a good job and tried to make a European version of a common American 5 tube circuit that was popular from about 1941 to the end of the vacuum tube era in the USA. The "All American 5" circuit used a "pentagrid" (heptode) converter, a "remote cutoff" pentode for the IF (intermediate frequency) stage, a combination diode / triode tube for the detector and first AF Amp and a power pentode for the audio power output amp. The DC for the set was provided by a rectifier. The original Philco 54C was an early version of this circuit. It seems that the person rebuilding this set also replaced the IF transformers and all capacitors and resistors. Nothing other than the tuning capacitor, speaker and the chassis itself is original.
The filaments (heaters) for these tubes are wired up in series. if the total operating voltages of these heaters in series did not add up to power line voltage, then resistance had to be added to compensate for this. In the US, the popular tubes were a 12SA7 (converter), 12SK7 (IF), 12SQ7 (Detector / 1st AF) 50L6 (Output) and 35Z5 (Rectifier). These heater voltages added up to approximately 120 Volts. The original 54C had heater voltages that added up only to 68 volts at 300 mA so sufficient resistance had to be added to make up the mains voltage.
It seems that the only original parts that remain in this set are the chassis, speaker and the tuning capacitor.
My recommendation is to make a note of the tube types used in the modification to your set. Feel free to list the numbers on the tubes here. Thee appear to be European 7 pin or 9 pin miniature tubes. If they have the same functions as listed above, try to trace out the current diagram based on the tube diagrams for the tubes used. The circuit may be legitimate. Do change out the electrolytic capacitors. Everything else should be OK, but you have to determine, based on the total heater voltages and any resistors in series with the heaters (they may have used a motor capacitor instead of a resistor) to determine the voltage that the original rebuilder designed this radio to operate from.
THE ONE BIG ISSUE HERE IS SAFETY!!!!
Radios of this type have their chassis connected to one side of the power line. Worse, that usually happens through the power switch making the radio to be dangerous no matter how the plug is inserted. I assume that in Europe, one side of the power line is at "Earth" ("Ground") potential If your mains voltage is in the order of 220 volts, this makes it even more dangerous. The original Model 54C had an interlock to completely disconnect power when the back was removed.
Here is a link to a very good article on this issue:
https://antiqueradio.org/safety.htm
If you can't get to this document or need it translated to Espanol, let me know.
Good luck and God Bless!
"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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