ECC804

The ECC804 is a general-purpose twin triode with identical sections and an internal inter-section screen. The March 1962 Brimar datasheet specifies AC or AC/DC television receivers. Photographs document Mullard, Mazda and Pinnacle specimens, some marked both ECC804 and 6/30L2. This double marking is concrete evidence of commercial naming, but does not automatically extend every rating to all other historical equivalence-list entries.

The heater requires 6.3 V at 0.3 A. For each section Brimar gives anode 200 V, grid bias −7.7 V, anode current 10 mA, transconductance 3.4 mA/V and amplification factor 18. Curves separately show current and transconductance versus grid voltage, plus anode characteristics. The factor 18 characterises the triode under stated conditions; complete-stage gain also depends on circuit and load.

Maximum anode dissipation is 2 W for either section but only 2.5 W total for both. The datasheet makes these ratings dependent on circuit and grid-cathode resistance: with cathode self-bias, that resistance must not exceed 0.25 MΩ for the quoted values. Maximum anode voltage is 250 V. Maximum heater-cathode voltage is 150 V RMS, referred to the higher-potential heater pin. These conditions belong with the figures.

The internal screen also has a requirement: its potential must not be positive relative to either cathode. The capacitance table separates holder-compensated values from totals including a B9A ceramic Carr Fastener 77/076 holder. For example, each section’s anode-grid capacitance changes from 2.5 to 2.8 pF, first-section grid-earth from 2.5 to 3.5 pF. The document defines earth by specific connections of other electrodes, heater and shields to cathode; these capacitances are measurement-condition dependent.

The base is nine-pin B9A. The drawing assigns 1/2/3 to anode/grid/cathode of one section, 6/7/8 to those of the other, 4/5 heater and 9 screen. Follow the numbered original’s orientation. Mounting is unrestricted; the drawing gives maximum bulb height excluding pins 49 mm and maximum diameter 22.2 mm. Approximate net weight is 0.5 oz; individual photographic specimen sizes remain distinct from datasheet maxima. Documentation: Brimar Valves ECC804, General Purpose Twin Triode, Thorn-AEI Radio Valves & Tubes Ltd., March 1962, Issue 2, pages 1–4, ratings, capacitances and characteristics.