C443N

The Philips Miniwatt C443N is a radio output pentode with directly heated filament, 4 V, about 0.25 A. Our historical sources place it around 1930 as a C443 development, output rising from 2.8 to 3 W but bias becoming substantially more negative, about −25 to −42 V. This family history does not justify transferring the C443 operating point to C443N. The N suffix should be retained when comparing circuits and data.

The Philips booklet combines different tables. The first gives maximum plate 300 V, screen 200 V, normal plate current 20 mA, approximate bias −45 V, normal transconductance 1.4 mA/V, maximum 1.8, amplification factor 32, internal resistance 23 kΩ. A second C443N table instead gives about −42 V, normal transconductance 1.5 mA/V, same maximum 1.8, factor 37 and internal resistance 25 kΩ. Associated curves repeat each set. Differences remain attached to their tables without inventing a construction change or chronology unexplained by the pages.

The supplement marked 3/4/33 distinguishes maximum-voltage symbols Va0 400 V and VaL 300 V; screen Vg′0 400 V and Vg′ 200 V. Maximum plate dissipation 6 W, screen 1 W, cathode current 25 mA. Mean screen current 0.4 mA, approximate limits 0.1–1 mA. Mean values, spread and maxima are different quantities. Grid-current onset is marked −2 V with filament 4 V, not interpreted as cutoff voltage.

Useful output is given into plate load 15 kΩ: 1.9 W with 13 V RMS drive, 3 W with 20 V RMS. The page assigns no distortion percentage to these figures, so none is added. Plate dissipation 6 W is not another output rating. Plate-grid capacitance 1 µµF, plate-cathode 10.8 µµF, grid-cathode 8.8 µµF equal 1, 10.8 and 8.8 pF. Two grid-circuit resistance limits are also listed, Rg1 1.5 MΩ and Rg2 1 MΩ, without their distinguishing conditions explained on that page.

The plate-characteristic chart uses screen 200 V and filament 4 V AC. Curve families show bias effects and the 6-W dissipation hyperbola; an axis extending to 600 V does not increase table operating limits. Likewise high currents near zero grid do not replace the stated cathode maximum. The graphs explain the pentode while keeping represented characteristics separate from permissible operation.

Tables give maximum overall length 89 mm, diameter 51 mm, base code O35, connection diagram S VIII. Retained descriptions identify a European five-pin base. This booklet references the diagram code without reproducing a numbered table, so no pinout or upper connection is invented. Dimensions are recorded with Philips/page attribution. Documentation: Philips Miniwatt C443N, six-page booklet with two technical tables and corresponding curves, supplement marked 3/4/33 and plate-characteristic chart. Data from the distinct C443N-Serie250 designation are not transferred here.