[thirtiesradio]

Thanks Bob. Did you do the electrical restoration on your set? I've never heard a restored 37-690 but I've read where they sound as spectacular (or maybe a bit better) then the 1938 model.

[y2kbruce]

Of all the 100+ consoles I have sold in the past 6 years the only one I have regretted selling was a minty 37-690 but it went to a very good home with someone we know here.

[thirtiesradio]

I know the 37-690 you are talking about y2kbruce. Very nice set! It was that set, when posted here that prompted me to find one

[Bob Andersen]

No, I haven't touched my set yet. It was stored in a garage for years and the finish is flaking badly, but the chassis look complete and in good shape.

[thirtiesradio]

Here's a rear photo of the set. Very dusty but clean under the dust and it is a working set. The set is completely original except for one thing......
if you look to the right of the speaker you will see the output transformer that is taking the place of the one on the speaker. I checked and the transformer on the speaker is still perfectly good!

The one mounted is a OTC LS-57 (with an unusual side mount)which is highly wanted by people who build triode tube amplifiers. Very strange that this is on here and that it uses the exact same type and color of wire as the original speaker/transformer. These transformers sell in the $300 - $500 range. Why it is on here when the other is perfectly good, and AM has a limited frequency response is a mystery.

[thirtiesradio]

Well someone wanted the hum gone as the radio is fitted with Philco branded 6A5G output tubes. The interstage transformer on the bottom chassis has also been changed to a UTC LS-21. A very nice and desirable transformer. I'm going to have to listen to it when restored before anything is changed back to original. I have all the original parts to do so if wanted but this set up may be better than when the radio was new.

[Mondial]

Looks like someone wanted the best possible sound from that set and cost was no object. Those UTC transformers were the finest available and were very expensive even when new. Even with AM's limited audio frequency range, the improved bass response of these transformers would be noticeable. It appears that the mods were done early in the radio's life as UTC painted their transformers gray by the 1950's.

The 6A5G's are great tubes with their indirectly heated cathodes, are really what should have been designed into the radio in the first place.

It appears that the person who modified this radio really knew what they were doing.

[thirtiesradio]

Hi Mondial. You are absolutely right. I looked and the UTC transformers were very expensive when new. The mods were professionally done and do look like they were done early in the radios life. If for a repair, there were many cheap transformers that could have been used that would have worked in the set. Someone modded this set to squeeze the best possible sound from it. It's going to be nice to hear it when restored

[Mondial]

Yes, it will be really interesting to hear it when done. What you have now appears to be the ultimate pre negative feedback PP triode audio amp. Those LS transformers were guaranteed to be flat between 20 Hz to 20 KHz to within 1 dB.

It looks like some of the electrolytics may have also been replaced with the more modern twist-prong FP types at some time.

You might get some idea of when the work was done by looking at the date codes of the 6A5G's. They appear to be late 30's or 40's manufacture. The codes are located on the base to the right of the PHILCO logo.

[thirtiesradio]

Thanks for the information Mondial. I looked at the 6A5G tubes and they have a U over a 9. Is that 1939 or 1949

[Mondial]

It depends.Take a look at the 6A5G stamp in the octagon on the side of the glass. If there is a date code stamped directly below such as A9M then it is definitely 1949. Also a 1949 date code on the base would probably be something like 926.

If there is no date code directly below then most likely it is 1939. Just looking at the photo and the U9 code, my best guess would be 1939.

[thirtiesradio]

Thanks. Here is what is on both tubes. I'm guessing 1939?

[Mondial]

Yes, it definitely looks 1939 production.

[thirtiesradio]

Thanks for the help Mondial!