[jmac3ky]

Several times over the years I have replaced rare glass tubes with available metal tubes. When they are shielded, many of the sets like Philco have a bottom part of the shield that surrounds the socket. The metal tube won't fit through the base shield opening. The rivets must be drilled out and the entire shield removed, ruining the original look of the chassis. I recently found one lone adapter that goes through the small opening at the shield base and then extends about an inch to another socket. The metal tube easily plugs in and the original tall shield can be placed around the metal tube without touching it.

Does anyone know where you can purchase such adapters?

[whirligig]

Try searching Ebay for "vacuum tube socket saver", "vacuum tube exten*", or "vacuum tube test socket". These thing were normally found in tube caddies and tool boxes of TV/Radio repairmen.

[jmac3ky]

Thanks a lot. "Vacuum tube socket saver" did the trick on ebay. Just placed an order. John

[jmac3ky]

Murphy's Law kicked in. The socket savers arrived and they were too large to fit in the tube shield base. They were
1 1/4" in diameter. They needed to be 1 1/8" like the original Philco tubes at the bottom. I have had a socket saver in the past that was more narrow, so they do exist. I'll lay out a couple of tubes to show the difference in width. It's still a neat concept if you wish to make a radio look original (shields and all) while substituting a later glass or metal tube.

[Arran]

Mostly this is not an issue when the set uses the old style based tubes such as a 6A7 or a 75, those are fairly easy to find and in the Philco sets that use these the tube shield base rarely gets in the way of an adapter since the older style tube bases are usually larger in diameter to begin with. Where you get into trouble is with the octal based "G" style tubes, on the 1937 models this isn't a problem, but on the 1938 models Philco purposely made a tube shield base that will not accept metal tubes, only "G" style octal tubes. In my opinion this was a vindictive move to prevent metal tubes, which were a G.E invention but heavily promoted by RCA, from being used in Philco radios since the 1937 models do fit them. 
 One issue with socket savers is that they tend to be made for tube testers or audio tubes, so the pinout may not work with something like a 6A8G or a 6K7G. You may have to get an empty octal tube base, and an octal socket and make up your own adapter, the China venders on fleabay sell lots of those, but get the measurements of them first. The reason I suggest getting an empty octal tube base is that desoldering pins on a dead octal tube is a real PITA, on the old style four, five, six, seven, and even eight pin bases it's relatively easy to do as the pins are larger. I was thinking of getting some to make adapters to replace Rogers 2X3 and 2Y3 rectifier tubes, which were used in pairs, with something like a type #80 or a 5Y3, in these cases the diameter of the tube base is not important since these rectifiers don't need a shield.
Regards
Arran