Klausmobile Tube Tester Files

Svetlana, year unknown. Also produced as Svetlana EF86. All triode mode stock parameteres taken from www.svetlana.com EF86 datasheet and application notes.

Triode mode, grids 2 and 3 at plate

Standard specifications per each triode
Parameter Maximum Operating Point * Measured **
Ua, V +300 250V 170
Ug, V - - -4.5
Ia, mA 6mA 0.65 1.2
Pa, W 1W (+0.2W Grid 2) (0.2) 0.21
Gm, mA/V - - 1.2
Rp, kOhm - - 27
Mu, V/V - 25 32

(*) Although Svetlana tables recommend 3.9kOhm cathode resistor (for auto bias), their app note - drawing below - recommends 1.5kOhm. Which is correct? see the 2mA load curves.

(**) Alternative DC point for higher currents looks like : Ua=210V, Ia=4mA, Ug=-4V (R autobias=1k), S=2.0 mA/V, Mu=36, Rout=17k, Rload=47..75kOhm (B+ = 400..500V DC). Watch the second grid power, anyway.

Full power curve (here and below "Plate current" is actually a sum of Plate, Grid 2 and Grid 3 currents).

As you can see above (load curves derives from "figure 3") - with 1.5 kOhm autobias resistor (Yellow dots for DC point) grid level is too high, and there's no way this setup can drive 40V RMS without grid currents (and high distortion). With 3.9kOhm autobias (Green dots for DC point) it's much better balanced! Gain is around 25 as in their data.

Triode mode, grid 2 at plate voltage, grid 3 at cathode voltage

It really doesn't change a lot! Just a downward shift in effective control grid voltage.

Legend: White curves: Ig<5uA Yellow: 5<Ig<20uA Red: 20<Ig<300uA. Measurements terminate at Ig>300uA

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