AM2

The Philips AM2 combines a low-frequency amplifier triode with a fluorescent tuning indicator. This magic eye has two shadow zones and an indicator control grid separate from the triode grid. The 4 July 1940 sheet specifies indirect heating at 4 V, 0.32 A with parallel AC supply. The typical triode point at plate 250 V and grid −3.5 V gives plate current 3 mA, transconductance 2 mA/V, internal resistance 25 kΩ and amplification factor 50.

An AM2 feature is two documented ways to control the luminous pattern. With target and triode plate fixed at 250 V, changing indicator grid from −5 to 0 and +3 V gives a luminous-sector angle of 5°, 150° and 160° respectively. Alternatively, with target 250 V and indicator grid 0 V, moving triode plate from 0 to 250 V changes the angle from 95° to 150°. Angles are measured at the screen edge and describe the bright sector, not shadow width. These are separate conditions, not superimposed data.

The 1940 limits are triode plate voltage 300 V, plate dissipation 1.5 W, target voltage 150–250 V, maximum target current 1 mA and cathode current 12 mA. Plate and target also have a separate no-current value of 550 V. Maximum resistance in either grid circuit is 2.5 MΩ; heater-cathode values are 20 kΩ and 50 V, the latter DC or RMS AC. Grid figures −1.3 V for triode and −1 V for indicator are associated with +0.3 µA current, not universal display-closure thresholds.

The file also contains sheets and curves dated 20 October 1937. Philips refers to C/EM2 curves and states electrical identity between AM2 and C/EM2 except heater ratings. This manufacturer-qualified comparison does not remove the need to check heater supply. Curves show triode behavior and indication as the two control voltages change. Our archive sources also report AM2 sales under the Telestar label in Finland, a commercial note distinct from Philips technical values.

The base has eight side contacts, P8A family. The diagram distinguishes cathode, heater, triode grid, indicator grid, fluorescent target and common plate/deflection-plate connection; contacts are not numbered, so numbering is not copied from another magic eye. Version-specific dimensions: the 1937 sheet gives maximum diameter 31 mm, the 1940 sheet 37 mm; both show maximum length 75 mm and a 30 mm base. Observations remain separate. Documentation: Philips Miniwatt, AM2, Triode L.F. Amplifier and Tuning Indicator with Fluorescent Screen, 4 July 1940, and AM2 Tuning Valve sheets dated 20 October 1937, six-page file. Dates document the consulted sheets, not by themselves introduction.