PM202

The PM202 is a Mullard output triode for battery receivers. The manufacturer presents it for three- or four-valve sets and markets it as Super Power. The application text compares it with the PM2A, saying it handles greater signal voltage and can drive a large loudspeaker at good volume. That description belongs to its contemporary receiver context; the trade name is not a modern wattage specification.

The directly heated filament requires 2 V. The preserved Mullard page gives current 0.2 A, maximum anode voltage 150 V and optimum load 3,700 Ω. Some input texts instead give filament current 0.3 A and an example with a 4,500 Ω load. These remain separate from the primary page's data: the currents are not treated as a tolerance and no unsupported chronological order is assigned to versions. Optimum load is the electrical load seen by the anode, not output-transformer DC resistance.

The manufacturer's characteristic table specifies anode 100 V and grid zero. It gives anode impedance 2,000 Ω, amplification factor 7 and transconductance 3.5 mA/V under those conditions. They describe one measuring point; stage gain also depends on the external circuit. Anode curves at different negative grid voltages carry three separate limits: DC anode voltage 150 V, DC anode current 20 mA and dissipation 3 W. Dissipation is not audio power available at the speaker.

For bias, Mullard gives approximately grid −7.5 V and anode current 10 mA at anode 100 V. At 125 V, negative bias ranges from 9 to 10.5 V with approximate current 14 mA; at 150 V, bias is −12 to −15 V, again with stated current about 14 mA. These are application guidance with explicit ranges, not a single grid voltage for every supply. The curves show current depending on both anode voltage and bias.

Preserved specimens show balloon and shouldered envelopes. A close-up reveals the wide box anode, grid and filament supports. The European four-pin B4 base has, according to the preserved connection table, pin 1 anode, 2 grid, 3 and 4 filament. A triode has no screen grid to supply. The available Mullard page has no mechanical dimensions; individual specimen appearances and descriptive measurements have not been turned into one nominal geometry for all PM202s.

Documentation consulted: Mullard, Type P.M.202, Super Power Output Valve, page 13 of the preserved bundle, with data, characteristics, anode curves and their marked limits, application and bias table; photographs of balloon and shouldered Mullard PM202 specimens.