Classic Hifi Care

Hello, So I was looking at sockets for the rectifier tubes in the CG . I have a couple of questions. In the one Sams I have the rectifier tubes are 5U4 In my other Sams its 5U4GB. Tubes look the same. Next question is, how do I find out what socket the 5U4 tube uses? Also what is an octal tube? Thanks in advance.

Hydrolastic wrote: ↑Mon Nov 07, 2022 3:32 am Hello, So I was looking at sockets for the rectifier tubes in the CG . I have a couple of questions. In the one Sams I have the rectifier tubes are 5U4 In my other Sams its 5U4GB. Tubes look the same. Next question is, how do I find out what socket the 5U4 tube uses? Also what is an octal tube? Thanks in advance.

Most of the suffixes indicate different envelopes--different shape of the glass, or a metal tube. Sometimes there are slight differences in tube characteristics. The tube manual tells about it. The old RCA manuals are probably online; I use my very old paper version.

Octal tubes are the ones with 8 pins and a center key; they usually have a Bakelite base. Early tubes had 4, 5, and 6 pins but no center key for alignment. Later tubes included the Loktals that Philco loved (8 pins, but with the pins emerging from the glass envelope like later miniature tubes, and a center key that locked into its base).

The 5U4 has a 5 volt heater so it will have a separate power transformer filament supply winding. The standard color code for the 5 volt winding is yellow. Look for the two yellow wires going to a tube socket.The other tubes will likely be 6 or 12 volt. And most schematics also have a tube diagram.

Chris Campbell

the "GB" as chris said is just a mod or a improvement on the design of the tube I.E. filament winding change... another example... the 6X5 rectifier is well known for taking out transformers... but you can sub the 6AX5 and it will play fine and not short and kill the transformer... I use them in my Zenith radios that call for the 6X5...

Hello, Thanks for the info on the suffix's now I have to find out the codes/names for the sockets. Where do I find that information? Tube manual?

As far as appearance, the original version of 5U4 is the older shoulder-style tube that came out in the '30s, I have a couple, they look cool like a smaller version of a WE 300B, whereas the 5U5GB has the newer straight glass envelope.

Here are a couple of reads that I found helpful:

https://www.vivatubes.com/identifying-v ... -eia-code/

http://www.tubebooks.org/

Bill