Vacuum Tubes for Vintage Radios
(1920s - Early '30s Tube Info)



Some notes on 1920's tube numbers, types  and bases

Vacuum tube numbers were not standardized until the early 30's. At that time all the prefixes such as "UX". "UY" and other pre-fixes were dropped. Examples:

No. UX-201A became a "01A", a UY-227 became a "27" and so on.

An "A" suffix on tube number indicated an improvement over the previous version, either version will work.

Some early tube
 numbering examples

00A, same as UX200A
01A, same as UX-201A
301A, etc, same as 201A
C-11, same as WD-11

12A, same as UX-112A
71A, same as UX-171A
80, same as UX-280



early    battery    tube
basic   specifications:

UV/UX-200 (00)
gas filled triode detector
filament: 5 volts 1A tungsten

UV/UX-200A (00A)
gas filled triode detector
filament: 5 volts .25A throated

UV/UX-201 (01)
triode AF/RF amplifier
filament: 5 volts 1A tungsten

UV/UX-201A (01A)
triode AF/RF amplifier
filament: 5 volts .25A thoriated

UV/UX-199 (99)
triode AF/RF amplifier
filament: 3 volts .25A thoriated

triode AF/RF amplifier
filament: 1.1 volts .25A coated filament, special base

electrically the same as the WD-11 except for the "UV" base

More Comments

The standard #27 was originally designated as "UY227" by most manufacturers, #45 was a "UX245". Some dropped the letter designations and simply went by 227 and 245 for the subject tubes.

The differences in the "ST" & "Antique Globe" style tubes are strictly cosmetic. The "Globe" styles are the early style & less common. They command a higher price because they look more authentic when peering into the insides of the 1920's radios.

During the 1920's, there was no standard numbering system for vacuum tubes. Although the "201A" was the standard used in most battery operated radios for RF & AF amplification. The suffix "A" indicated a thoriated filament which drew less current than it's predecessor the 201 which had a 1 amp, tungsten filament. The 201 with it's 5 volt tungsten filament lit up like a light bulb  whereas the "A" version with it's 1/4 amp filament produced a dull, warm orange glow.

Many manufacturers had their own prefix designation for the "201A". For the RCA "Radiotron", it was UX-201A, Cunningham was CX-301A, Montgomery Wards; GX-201A and there were many other variations by brand name and some brands had their own numbers.

The UX, CX, DX etc, simply indicated standard 4 pin, plug-in base. This "UX" applied to other 4 pin tubes as well such as UX171A, UX-210, UX280 and any 4 pin plug-in tube. The UV prefix was for the bayonet version (stubby, short pins) that required push & twist to lock in place. The tube sockets in many radios would accommodate either UX or UV based tubes. In the early 1930's tube numbers were mostly standardized, the prefixes were dropped and nearly all of the 1920's tubes were now designated with two digits. The famous 201A was now an "01A", UX120, was now a 20, the 280 became an 80, 210 a 10 and so on.

More valuable info > on tube testing.

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Below are images of some of the early vacuum tubes

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© C.E. Clutter


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Northwest Vintage Radio Society

Member of:
Antique Wireless Association