[morzh]

I have at least two shield bases hacked on my chassis. One is totally torn off due to using a metal tube on it, but at the same time they did not provide the GND to the tube's case, so I soldered the GND to the respective pin. Otherwise I'd have to drill out the rivets and find a base to install.

[Ron Ramirez]

...why did Philco use the enclosed bases in the 1936 models, use the open shield bases w/clips in 1937 then switch back to the enclosed bases in 1938?

Well,

in the 1936 season Philco was still using the standard base tubes. All of the small signal standard base tubes (not counting audio output tubes or rectifiers) have the same size base and easily fit into the tube shield base; size was not an issue with these.

Beginning with the 1937 season they switched to octals, and those 1937 tube shield bases made it easy to use metal tubes as replacements.

Now as to why Philco switched back to the 1936 style base for the 1938 season, we can only guess because this is another of those questions that only dead Philco engineers can answer positively. And dead men tell no tales.

So here are my theories.

A. Philco did not want people using metal tubes in their radios. The animosity between Philco and RCA could have been the basis for such a move (a dumb move when looking back through history).
B. Philco discovered that the bases of the small signal G tubes were the same size as the small signal standard base tubes and, possibly still having an inventory of 1936 style tube shield bases, switched back to save money.
C. Both of the above.

I would pick C. By using the 1936 tube shield bases, they could use up their old inventory of bases and keep anyone from using metal tubes as replacements. Or, at least, make it extremely difficult to do so.

Of course, we know that many of these were bent open, cut open, or even removed so that metal tubes could be used.

[Kenradio]

Here's some pictures of the 37-690 working--I'm very pleased with the radio and the crackling isn't as bad at the moment. I barely have to turn the volume control as it is loud and has plenty of bass.  Ken

[tbone]

Great work! You are so lucky to have a radio in great physical shape to start with. It’s nice to see another one saved.

[Phlogiston]

...why did Philco use the enclosed bases in the 1936 models, use the open shield bases w/clips in 1937 then switch back to the enclosed bases in 1938?

Well,

in the 1936 season Philco was still using the standard base tubes. All of the small signal standard base tubes (not counting audio output tubes or rectifiers) have the same size base and easily fit into the tube shield base; size was not an issue with these.

Beginning with the 1937 season they switched to octals, and those 1937 tube shield bases made it easy to use metal tubes as replacements.

Now as to why Philco switched back to the 1936 style base for the 1938 season, we can only guess because this is another of those questions that only dead Philco engineers can answer positively. And dead men tell no tales.

So here are my theories.

A. Philco did not want people using metal tubes in their radios. The animosity between Philco and RCA could have been the basis for such a move (a dumb move when looking back through history).
B. Philco discovered that the bases of the small signal G tubes were the same size as the small signal standard base tubes and, possibly still having an inventory of 1936 style tube shield bases, switched back to save money.
C. Both of the above.

I would pick C. By using the 1936 tube shield bases, they could use up their old inventory of bases and keep anyone from using metal tubes as replacements. Or, at least, make it extremely difficult to do so.

Of course, we know that many of these were bent open, cut open, or even removed so that metal tubes could be used.

How about the use of pin 1 for something other than ground?

[Ron Ramirez]

Good point, but did Philco do that in 1937 or 38? I can't recall any such instances...I'm not saying they didn't, just that I do not remember...

...geez, as I get older I remember less...

[Kenradio]

Hello everyone, I'm almost done with the radio--just waiting for the 2 resistors from the auction site to replace the 3000/2240 ohm candohm and I should be done. I touched up the alignment this morning on the receiver chassis and all of the bands are now accurate with the dial with excellent sensitivity. I didn't have to adjust the I.F. or magnetic tuning transformers and the magnetic tuning (AFC) is working correctly. I was curious why Philco decided to have the bass amplification circuit disabled on the 4 shortwave bands? On AM it works great but on the other bands it is disabled--the other bands sound very good with lots of volume though. I'm glad at least I don't have to work on the cabinet as it is in excellent shape .     Ken

[tbone]

It would be great to see pictures of your radio all together in the cabinet when finished, if you have time.

[Kenradio]

Good morning Tony (TBone), almost done with the restoration--got the 2 resistors Saturday to replace the bad candohm in the power unit. I'll be working on it Tuesday installing the resistors and should be able to put it all back together this Friday (5/25) and I'll take pics of the front & back of the radio working.  Ken

[Kenradio]

Good morning, finally done with the power unit restoration and reinstalled the receiver chassis back into the cabinet, replaced the fuses with the correct ones and powered up the radio and it is working great on all bands and has plenty of volume. Only issue is the chassis grommets that support the receiver aren't tall enough so I'll have to order taller ones from Renovated Radios later today. I'll be replacing the speaker wire harnesses at a later date as they are dried out and starting to crack through the insulation--the power cables from the receiver are in excellent shape. I have pictures posted below of the 37-690 in operation. I saw that Ron has started to restore a 38-690 so I'll be watching the restoration with interest.    Ken

[WyTex]

Looks great!
Congratulations!
Those 690's are just gorgeous.

[morzh]

Ken

Great job. Anyone who tackled any 690 successfully deserves praise.

[Kenradio]

Thanks Paul & Mike(Morzh) I have restored other Philcos in the past but this was the most challenging. I took my time and took lots of pictures and printed out the service bulletin which was a big help. I did find a little bit ago the proper 3/8" high rubber receiver chassis support grommets so that should take care of the height issue. All I need to do is to fabricate a bottom cover for the receiver chassis. Soon I'll be starting on my 37-116 cabinet which needs to be stripped and refinished (not looking forward to that).   Ken

[KCMike]

Great job Ken.   That was a lot of work!

[morzh]

You could start it without the cover. It's not like someone will try to reach in there.