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Qty 2, Sylvania 884 Thyratrons, NOS - New Old Stock. These tubes are unused and tested just dandy. They will come in their original, but decaying boxes. Tubes have been tested. The 884 (gas triode) thyratron is equivalent to the 6Q5. VT-222 and CV647 are its U.S. and British military designations, respectively. This thyratron can be used in "relay service" (driving an electro-mechanical relay), but its mostly used in "sweep generator" circuits, in old oscilloscopes (aka oscillographs). Its Anode Breakdown vs Grid Voltage curve indicates that this tube makes a nice VCO, as part of a tube sound synthesizer. This function is often done with a 2D21 gas tetrode, but ST shape of the 884 is much cooler than 2D21's miniature-7 package. NOTE: The 884 is the equivalent to the 6Q5, with both having octal bases and 6.3V filaments. The 885 (aka 2B4) is the 2.5V filament, 5-pin, counterpart. 2.5V filament voltage was the 1st attempt to standardize the filaments, switching to 6.3V later. If your oscillograph is really old it may be fitted for 2.5V tubes. Per the RCA datasheet, the 884 and 885 were primarily intended for sweep application. Relay service was a secondary use. I've used this tube as a timebase, syncing off the AC line, and its very stable. Complete datasheets can be found at: http://www.tubedata.info and Datasheets for 8xxx A tube synthesizer design can be found at: http://www.cgs.synth.net/tube |