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Tubes for Philco 80 Jr. - Printable Version

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Tubes for Philco 80 Jr. - Jim Dutridge - 06-08-2024

Did the 80 Jr use balloon or ST style tubes?

RE: Tubes for Philco 80 Jr. - MrFixr55 - 06-08-2024

Hi Jim,

Yes, the original 80 Jr used "balloon" style tubes. I can confirm this because I worked on one that had all Philco balloons. The original used the type 36 tetrode as an autodyne convertor (1st detector), and for the 2nd detector, the set used a 36 as a regenerative grid-leak detector. By this time, Philco used their own branded tubes, made by Sylvania. This 4 tube set continued as the 84 with ST type 77 pentode tubes for the 1st and 2nd detectors and 42 as the power output, and finally as the 37-84 using the octal based 6J7 as a 1st and 2nd detector and a 6F6 as the output tube.

The original 80 Jr caused a ruckus as it was introduced at $19.99 in the throes of the Great Depression. It was meant to be a "loss leader" to get people into the store, where the sales rep could attempt to upsell the customer to a better, high quality Philco set. Instead, they sold a over 200,000 of these. RCA had just introduced the R28 "Radiolette for $25.99 and had to further reduce the price when Philco introduced the 81 and dropped the price of the 80 to $14.95 complete with tubes! Compare this to the fact that most RCAs built before the depression cost at least $100.00, and some as much as $800.00 (more than the cost of 2 Model T Fords

RE: Tubes for Philco 80 Jr. - Hawkeye - 06-08-2024

The Philco model 80 instructions show that it was originally supplied with globe tubes.

https://philcoradio.com/library/index.php/documents/philco_docs/manuals/philco-80-instructions/

RE: Tubes for Philco 80 Jr. - Jim Dutridge - 06-10-2024

Thanks for the information. I kinda thought they would be globe since the one I just picked up had 3 out of the 4 tubes in that style, but I just wanted to be sure. Its too bad the 80 acts like it might be shorted and the 42 tests very weak.

RE: Tubes for Philco 80 Jr. - David - 06-10-2024

Rule of thumb the output and rect tubes will need to be replaced. The output tube as a single at very low volume will draw about 1/2 the current of full volume. The rect is always working hard. Like to run my sets at 105-110 volts the tubes will be happy and so will my wallet. David

RE: Tubes for Philco 80 Jr. - Steve Davis - 06-10-2024

Quote: The output tube as a single at very low volume will draw about 1/2 the current of full volume. 

This is incorrect, a class A amplifier will draw the same current no matter the volume level.

Steve

RE: Tubes for Philco 80 Jr. - MrFixr55 - 06-11-2024

The 80 acts like it is shorted?  If you see flashing inside the 80, shut it off immediately!  It is likely that there is a short loading the rectifier down.  The most common cause is shorted electrolytic capacitors.  The originals of this vintage almost never survive and will short.

All caps on antique radios should be replaced with new, modern caps, but replacing the electrolytic caps used as filters in the power supply is an absolute must, especially in radios from the 1930s.

It's a shame if the 42 is too weak to use.  Globe 42s are way cool in my book.  They are the genesis of what became the 6F6, a common pentode (non-beam power) audio output tube.  ST type 42s are common, but globe 42s are rather rare and a good one will command some money.  Save your old one for display.

RE: Tubes for Philco 80 Jr. - David - 06-11-2024

Some info. David   https://audioxpress.com/article/you-can-diy-build-a-single-ended-guitar-tube-amplifier