201A Radio Tubes
by Hal Kravig
The 00 and 01 through 99 tubes were among the first commercial tubes manufactured by the industry to try to standardize wireless vacuum tubes in 1919 or so.The first tubes were either globular, tennis ball or cylindrical shaped and had wire leads or short pins (UV Based, all pins the same size) and Brass Based with tips at the top where the vacuum was made, and then the tubes progressed to remove the fragile tip and add longer pins with two large pins and two small pins (UX Based) for better orientation, and then came Bakelite bases, and then shoulder tubes (ST shape) that were also called coke bottle shaped.
The thought was that 00 thru 99 would cover all tubes that could be made never knowing what radio and audio would become.The prefix 1 as in 100 or 101 meant the manufacturer National Union or Ken-Rad, e.g., 200 and 201 meant RCA, 300 and 301 meant Cunningham, 400 and 401 meant DeForest.The first tubes had 5 volt and 1 amp filaments that burned out quickly and consumed your battery supply very quickly. So the industry switched to 1/4 amp tubes and added the A suffix to denote the lower filament current and later added 1/8 amp tubes, B suffix, and even 1/16 amp tubes, C suffix.
Along the way it was learned that poor vacuum caused the filaments to form an oxide on their surface so tube rejuvenation was vogue to burn off the rust that formed on the filaments and improve emissions to restore the tube.This was done by applying a higher voltage to the filament for a short period, e.g., raise voltage from 5v. to 7v or 8v for 60 seconds to burn off the rust. New filament materials were tried and alloys developed, even platinum, to combat this problem but the solution was just to have a better, cleaner vacuum.
Manufacturers must either more fully evacuate the tube or burn off the oxygen that was left inside the sealed tube are two techniques that were employed. The burn pan was built into the tube (getter pan) and filled with magnesium or other ignitable powder and like an early flash bulb the oxygen inside the tube was burned off and a silver deposit was left coating some or all of the inside of the tube. This is called the getter in the tube. Western Electric tubes were better manufactured and often you will see good tubes with little or no getter.
Licensing of other manufacturers and theft by manufacturers caused many brands to be initiated often using very similar names, e.g. Cleartone, Clear-Tone, Cleartron, Kleertron, Cleantron, etc.I keep a list that now has about 750 brands of the 01A and I personally have about 500 different brands. In 1934 a new tube numbering system was developed called the RMA (for Radio Manufacturers Association) standard numbering system where the tube numbers described the tube, the first number the filament voltage, the tube type and the number of elements, e.g. the 2A3, the 5A3, the 6A3 and the 12A3 were all the same tubes with 2v, 5v, 6v and 12v filaments, Amplifier types, and with three elements (triode).Some manufacturers like Western Electric ignored these changes and continued to use their own numbering system.
I collect early tube literature, tube advertising, and tube testers to display with my 01A collection and collect battery sets, particularly exposed tube, glass panel and glass cased battery sets that display the venerable 01A.If you ever run across any odd brand 01As let me know.
Regards, Hal Kravig, PO Box 341361, Memphis TN 38184 or call toll free (866) 237-7940 nights and weekends or (800) 859-4436 weekdays.
