08-18-2024, 09:04 AM
Hi Rich,
Welcome to the Phorum!
Type 80 tubes are very commonly available on both eBay and from suppliers that experts like RodB trust. 42s are slightly less common but are quite available. If the supply ever runs out, 42s can be replaced by octal based 6F6s with a socket change. Other than the base, these are the same tubes. If one looks up a 42 in the 1940 RCA receiving tube manual, it will state to refer to type 6F6 for specifications. Same for the type 80. 80s can be replaced by octal based 5Y3s with a socket change. However, I would not worry about this, as these tubes are in good supply. In fact, I have found or bought several RCA branded 80s (red lettering) that are indistinguishable from 5Y3s except for the 4 pin base. For "daily drivers", I prefer these tubes. For show and occasional play sets, use a globe or ST style tube depending on vintage.
The 42 and 80s first came out as globe tubes, which I find to be very cool. However, your set calls for STs.
Interesting that your set uses octal tubes for several stages such as the RF, convertor, detector- 1st AF, and the remote receiver. Apparently, Philco either had an abundance of 42s and 80s in stock or had either a hard to break contractor a great deal from their supplier (Sylvania?). Also, interesting that Philco used a 6K7 for the RF Amp but stuck with the 78 for the IF Amp. The 6K7 was the octal base replacement to the 78, but the interelectrode capacitances are different. Guess they did not want to change their IF transformers yet. Also, the 37 is a real old tube; the 6V filament version of the 27, the first heater-cathode tube, introduced in 1927!
No doubt about it, this is a cool set and with a thoroughly modern 5 watt Push Pull audio with cathodyne phase inverter, this should fill the room with great sound. When you get all working, consider adding an input jack for phone, aux, CD, MP3, etc. and enjoy that "great tube sound" from cleaner audio than you can get from an AM station.
Good luck with the restoration.
Welcome to the Phorum!
Type 80 tubes are very commonly available on both eBay and from suppliers that experts like RodB trust. 42s are slightly less common but are quite available. If the supply ever runs out, 42s can be replaced by octal based 6F6s with a socket change. Other than the base, these are the same tubes. If one looks up a 42 in the 1940 RCA receiving tube manual, it will state to refer to type 6F6 for specifications. Same for the type 80. 80s can be replaced by octal based 5Y3s with a socket change. However, I would not worry about this, as these tubes are in good supply. In fact, I have found or bought several RCA branded 80s (red lettering) that are indistinguishable from 5Y3s except for the 4 pin base. For "daily drivers", I prefer these tubes. For show and occasional play sets, use a globe or ST style tube depending on vintage.
The 42 and 80s first came out as globe tubes, which I find to be very cool. However, your set calls for STs.
Interesting that your set uses octal tubes for several stages such as the RF, convertor, detector- 1st AF, and the remote receiver. Apparently, Philco either had an abundance of 42s and 80s in stock or had either a hard to break contractor a great deal from their supplier (Sylvania?). Also, interesting that Philco used a 6K7 for the RF Amp but stuck with the 78 for the IF Amp. The 6K7 was the octal base replacement to the 78, but the interelectrode capacitances are different. Guess they did not want to change their IF transformers yet. Also, the 37 is a real old tube; the 6V filament version of the 27, the first heater-cathode tube, introduced in 1927!
No doubt about it, this is a cool set and with a thoroughly modern 5 watt Push Pull audio with cathodyne phase inverter, this should fill the room with great sound. When you get all working, consider adding an input jack for phone, aux, CD, MP3, etc. and enjoy that "great tube sound" from cleaner audio than you can get from an AM station.
Good luck with the restoration.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards,
MrFixr55
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