Higher-voltage power triode (mu 12, Pa_max 100 W, filament 10 V/3.25 A, top-cap anode); different electricals (lower mu) and higher dissipation — not a drop-in substitute
Cathode Current (max)Max-Signal DC Plate Current (Class B AF, ICAS)330mA
Typical Operating
Anode Voltage (typical)Plate Voltage (Class B AF typical, ICAS)1,500
Notes
Directly-heated thoriated-tungsten filament: the filament serves as the cathode; there is no heater-cathode isolation.
Top-cap anode: the plate connection is via a medium metal cap on top of the ST-19 envelope, not via a base pin. Pin 2 is No Connection.
Base is a medium-metal-shell small 4-pin bayonet (basing designation 3G).
gm and ra are not stated in the RCA datasheet; the values recorded here were derived from the published Average Plate Characteristics curves (RCA drawing 92C-6279, April 30 1941) near an operating point of Va = 1500 V, Vg = -100 V and are approximate. mu = 20 is the datasheet nominal (range 18-22).
Class B AF modulator (two tubes, ICAS): Va = 1500 V, Vg = -67.5 V, Ia(zero-signal) = 40 mA, Ia(max-signal) = 330 mA, plate-to-plate load 9800 Ω, Pout ≈ 330 W.
Class C RF telegraphy (ICAS): Va = 1500 V, Vg = -130 V, Ia = 200 mA, Pout ≈ 220 W per tube.
Grid-leak bias is the preferred bias method due to automatic bias adjustment under fluctuating load; if fixed bias is used at 1500 V plate, RCA recommends approximately -50 V fixed bias plus grid-leak.
Filament voltage tolerance is ±0.5 V (9.5-10.5 V).
Historically used in the McIntosh MI-200 200-watt audio amplifier (WWII / early post-war) where pairs of 8005s were run in Class AB/B push-pull.