6325

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• High-voltage industrial rectifier — PIV 2200 V and RMS plate-supply voltage 780 V per plate, well beyond common receiving-tube rectifiers. Peak inverse under full load at 780 V RMS supply is 975 V (per life-test data), with absolute PIV 2200 V.
• Classification: full-wave high-vacuum rectifier per Philco March 30, 1953 datasheet and GE 1973 Essential Characteristics. NOT a mercury-vapour or thyratron type — it is a conventional indirectly heated hard-vacuum rectifier despite the unusually high voltage rating.
• Heater current is high (2.7 A) to sustain the large cathode area required for the 250 mA DC output at elevated plate voltage.
• Filament voltage must be applied one full minute before plate voltage to allow cathode warm-up — applying plate voltage to a cold cathode will cause emission damage.
• Ruggedised: tubes withstand 450 g impact shock at 30° hammer angle (Taft-Pierce shock tester).
• Common-cathode topology (single cathode on pin 1) — conventional full-wave rectifier connection, not suitable for voltage doubling.
• Life-test data: 550 hr life expectancy ≥ 90%, 1000 hr ≥ 80%, at ambient 125 °C.
• Vdrop not stated explicitly in the datasheet. Datasheet Condenser-Input life-test point: Vac=350 V RMS/plate, Idc=125 mA per plate, Vdc=285 V. Ideal full-wave peak ≈ 1.41 × 350 = 494 V. Dataseet Choke-Input life-test point: Vac=780 V RMS/plate, Idc=75 mA, Vdc=650 V, Lfilt=4.5 H. Ideal DC with choke input = 0.9 × 780 = 702 V; measured 650 V → total drop ≈ 52 V including series resistance. Rs per plate 250 Ω × 0.075 A ≈ 19 V, leaving tube drop ≈ 33 V at 75 mA per plate. Recorded as approximate value derived from regulation table.

• https://frank.pocnet.net/sheets/201/6/6325.pdf
• https://www.radiomuseum.org/tubes/tube_6325.html