E415

The Philips Miniwatt E415 is an indirectly heated cathode triode for early AC-powered receivers. The Dutch Philips leaflet describes detector service, transformer-coupled audio amplification and RF amplification in neutrodyne circuits; the multilingual sheet adds oscillator service. The German catalogue documents use with the Philips 4003 audio transformer for 45-fold amplification: this figure applies to the described combination, whereas the valve amplification factor is 15. It is a useful detail for understanding contemporary transformer stages.

Heating voltage is 4 V: the German catalogue and Dutch leaflet give 0.9 A, the multilingual sheet approximately 1 A. The catalogue recommends the Philips 4009 transformer without an additional heater resistor under the illustrated conditions. It documents the five-pin O35 base with a centre cathode and the four-pin A35b variant with the cathode on a side screw. The 1999 compilation also shows the N base with a different arrangement. Identifying the actual connections is therefore necessary when choosing a version. The catalogue gives 92 mm length excluding pins and 52 mm maximum diameter; the sheet specifies maxima of 91 and 47 mm.

In the German catalogue the anode operates at 50–150 V, with 2 mA/V transconductance and 7,500 Ω internal resistance. At 150 V normal current is 6 mA and bias −6 V; to avoid distortion, −4.5 V is prescribed at 120 V. The Dutch leaflet instead lists 6.5 mA normal current and 2.5 pF anode–grid capacitance. The multilingual sheet gives 200 V maximum anode voltage, 6 mA normal current, approximately −8 V bias, normal and maximum transconductance of 1.4 and 2.4 mA/V, 11,000 Ω internal resistance and 3.5 pF anode–grid capacitance in its general table. These different conditions and presentations are kept separate rather than combined into a composite operating point.

The limit table, also present in a version dated 9 June 1933, distinguishes 400 V anode voltage at zero current from 200 V under the condition labelled VaL. Maximum anode dissipation is 1.5 W and maximum cathode current 15 mA. This table gives anode–grid, anode–cathode and grid–cathode capacitances of 3, 3 and 4.2 pF: the first differs from the general table’s 3.5 pF. Photographs of one specimen show a mesh anode and an upper transverse support; our sources describe this support as stiffening the electrode assembly and potentially helping reduce microphony. This describes the observed specimen, not a guarantee that every E415 has identical construction or is immune to vibration.