This throws things just a little off topic, but I have a list of EIA codes that were sent out with Sams in 1970, and this online list confirms it. My Motorola Quasar from about '73+ has a crt labeled Motorola & very clearly labeled "EIA Code 337". But that is for Westinghouse. I didn't know they ever made any color crt's, let alone after they gave up the TV business themselves c.1970. Maybe somebody else used that number later on?

Chad:

The 5V3 uses an octal socket configured the same as a 5U4. It has some higher ratings. I don't remember that it was used in anything but the Philco TV123.

Don

O.K., thanks for clearing me up. I have seen a lot of different 5 volt rectifier tubes recently in different equipment, 5X4,, 5Z3 etc and it can be difficult to remember what the lesser used ones are in base and rating.