EL804

The EL804 is an output pentode for wideband amplifiers, described in Telefunken and AEG sheets. A readily recognizable feature is the anode connection on top of the bulb, separate from the nine contacts of the Noval base. Indirect heating uses a 6.3 V, 700 mA heater suitable for DC or AC parallel supply.

The documented operating point gives anode 140 V, screen 170 V, anode current 70 mA, screen current 5 mA and transconductance 10 mA/V. Telefunken specifies a 160 Ω cathode resistor; AEG explicitly gives control-grid bias −12 V. Internal resistance is 14 kΩ and screen-to-control-grid amplification factor 9. This is a documented point, distinct from the curve families showing currents as voltages vary.

Limits include anode and screen 250 V, anode dissipation 10 W and cathode current 100 mA. Screen dissipation is 1.75 W, with a separate 4 W rating under drive: the latter is not an ordinary signal-independent limit. Telefunken gives maximum grid resistance 1 MΩ with automatic bias, 0.5 MΩ with fixed bias. Capacitances are input 13 pF, output 8 pF, anode-control grid at most 0.15 pF. The anode’s 10 W is heat dissipation, not a specified audio output power.

The connection diagram assigns pin 2 to control grid, 3 cathode, suppressor and internal shield, 4 and 5 heater, 9 screen; the anode is the top cap. Manufacturers prohibit using free contacts as wiring supports and require retention where needed. Both drawings give maximum diameter 22.2 mm, height above the base seating plane 76.2 mm including the cap, separate pins up to 7 mm and maximum mass 20 g. The top contact has a stated diameter of 6.35 mm.

Documentation consulted: Telefunken EL804, four pages of data, connections, dimensions and curves, with a sheet dated 1 September 1961 and a curve plate dated 2 January 1956; AEG EL804, March 1960, five pages. These dates identify documents, not automatically commercial introduction. Curves distinguish screen voltages of 170 and 200 V and describe behavior beyond the tabulated point, with dissipation limits still applicable.