American designation for PY500A — 42V heater, not compatible with 6.3V circuits
EY500
Earlier version with slightly different ratings — normally replaceable per radiomuseum
PY500A
Same tube electrically but 42V heater for series string TV sets — not a drop-in in 6.3V circuits
Electrical Specifications
Absolute Maximum
Anode Dissipation (max)Plate Dissipation (max)11W
Heater-to-Cathode Voltage (max)Heater-Cathode Voltage (max peak)6,300V
Rectifier
Peak Inverse VoltagePeak Inverse Plate Voltage (design centre max)5,600V
Voltage Drop (typical)Tube Voltage Drop (at 440 mA, derived from Ua/Ia = 45.5 Ω)20V
Heater
Heater VoltageHeater Voltage6.3V
Heater CurrentHeater Current2.1A
Notes
Magnoval 9-pin base (B9D) with top-cap cathode connection (6.35mm cap). Five anode pins (1,2,3,7,8) distribute the high continuous current.
Free pins not to be connected externally — do not use unused socket contacts as tie points.
PIV rating of 5600V applies when pulse duration does not exceed 22% per period (tmax 18 µs). Absolute maximum PIV is 7000V.
Absolute maximum pin temperature (tStift) is 140°C — adequate heat conduction through socket and socket contact springs must be ensured.
Special precautions must be taken to prevent the tube from becoming dislodged from the socket. Clamping on the cylindrical part of the bulb is not permitted.
Measuring value: Ua/Ia = 45.5 Ω at Ia = 440 mA, corresponding to approximately 20V drop at full rated current.
One of the highest-rated TV damper diodes available, with 440mA continuous current and 11W plate dissipation — popular in DIY audio power supplies for high-current applications.