[sdradioman]

I have a 38-116 that has the PP 6L6 output. It has glass 6L6's right now that test weak. I have a strong set of metal 6L6's. Can I use them or does there have to be wiring modifications going to a metal tube.

[Jim Koehler]

Since metal 6L6's came out in 1936, it would be perfectly feasible to use them as subs in your unit.

[klondike98]

Looks like they both use octal sockets with the same pin outs.

See:
http://www.nj7p.info/Tubes/SQL/Tube_query.php?Type=6l6

and

http://www.nj7p.info/Tubes/SQL/Tube_query.php?Type=6l6G

[Radioroslyn]

+1
Just double check pin1 on the chassis to be sure it's not used as a tie point as it's connected directly to the metal shield on the 6L6.

[Arran]

 Same tube, except that the 6L6G has a slightly higher output I think, but it probably won't matter, yes watch for pin one being used for things other then a ground, Philco liked to do things like that to punish people for daring to use metal tubes from the evil RCA. I'm surprised that your set doesn't have something goofy like a pair of 6B4Gs, which was the octal version of a 6A3.
Regards
Arran

[Steve Davis]

The best tube tester is the radio its self. If the radio works with the glass 6L6s, I would check the B+ voltage to make sure it is not too high because of low emission of the output tubes. If the B+ is within reason, then use your original tubes and keep your original look, they will probably last for many years. Remember, our tube supply is finite.

Steve

[TA Forbes]

Agree with Terry about the pin 1 issue. But other than that, you can use any 6L6 including the metal variants and the GB/GC variants. 

The military variants of the 6L6, especially the JAN/VT metal ones tend to test better than the ones made for consumer sets. 

[Arran]

 In actual fact, of all of the tubes out there, the 6L6 is one that is still in production in one form or another, although the envelopes are not the same as the North American made 6L6Gs. The Russian/Soviet 6P3 comes to mind, they have some in a GB style envelope, and some that are in a sort of bulged out GT style, they had a sort of ST version but they looked more European or British. I think that they Chinese are also still making 6L6s, possibly the JJ company in Slovakia, though I would stick with the Russian ones if going for new or NOS.
Regards
Arran

[TA Forbes]

Yes indeed, between the Russians and the Chinese we can now buy brand new 2A3s, 6A3s, 866As, 300Bs, and 6B4Gs. 

I am currently using two Chinese 2A3s in my Sparton 1568. I paid 28.00 a piece for them. They glow white.... probably because the tubes have (factory) 360V plate and -64 cathode, which means that with 120+V house service the voltages are a bit more. However they have been problem free thus far. 

Also got a number of the Chinese 6V6GTs when they were going for 8 bucks a pop, and again no issues thus far. Every one of them tested 4100uMho or more.