Valves/Tubes was: ez80

On 19 Jul 2010 at 21:11, Tony Duell wrote: I don't believe so. 6L6 = metal beam power tube; 6L6G = glass envelope. (not to mention GT, GA, GB, etc.). The problem with the pre-WWII receiving tube system is that there were several systems. For example, the hugely popular UV201A means a type 01 triode, with a UV base and a thoriated tungsten (A) filament. In the RCA handbooks, the tube is simply listed as type 01A. Each manufacturer also had their own system, so for instance, Hytron had HYxxx numbers, in addition to their own "GTX" ceramic based versions of popular tubes. Raytheon had their CKxxx numbers, which they carried over to the solid-state world (remember the CK722?). In 1934, the Radio Manufacturer's association set in place a new system, which is the one we know now (first number = filament voltage, letter (assigned like license plates, in order of introduction), number of functional electrodes. Like license plates, the numbers ran out, so manufacturers began using the last number on an as-needed basis. So we have 6B4G = power triode, 6B5 = dual internally-coupled triode, 6B6 = duplex diode+triode, 6B7 = duplex diode + pentode, 6B8 = duplex diode pentode. On the other hand, 1D5-GP is a pentode; a 1D5-GT is a tetrode. Of course, a 12AP4 doesn't have a 12v filament, but is a 12" CRT with a 2.5V filament and P4 phosphor. Transmitting and industrial application tubes are sui generis with lots of bizarre combintions. For example, an 866A is a mercury-vapor rectifier with a 5 amp, 2.5v filament and a 10KV PRV rating and a 1000 ma peak current capacity. On the other hand an 866Jr. is a half- sized version--sort of. The Taylor version has a 3 amp. filament and 3.5KV PRV with a 250 ma. peak current. The Hytron 866Jr has a 3 amp filament, but a 5KV PRV and a 500 ma peak current. As I said, it's like Boston. --Chuck