Klausmobile Tube Tester Files

Kaluga, 03/1975 - This dual triode looks and tests very close to 6N23P (ECC88), yet is wired differently, each half asymmetrical. Of the four tubes from 1970-80s that I checked today, two have nearly identical halves which I presume is how they should be. As is the case with 6N23P, there are two versions, 'closed plate' (1970-s) and 'open plate' (1980-s) with clear metal 'screen' flap. As is the case with 6N23P, the numbers in my databook seem wrong: specified 90V/15mA point cannot be reached at -9V bias, only at about -1V which is too high for a practical application. The tube showed no desire to oscillate at all. This seems odd since Franz Hamberger's site calls it 'RF Cascode Amplifier'; and a very similar 6N23P likes oscillating.

Standard specifications per each triode
Parameter Maximum Operating Point Measured 03/1975 tube
Ua, V +300 90 143
Ug, V -100 -9.0 -3.0
Ia, mA 20 cathode 15 10
Pa, W 1.8 1.35 1.4
Gm, mA/V - 12.5 9
Rp, kOhm - 2.8 3.9
Mu, V/V - 34 34

Looking at the curves, you see that 15mA/100V (Ug=1V) is too close to grid current zone to be practical.

1. Curve at normal Uheater, full operating power

2. Closer look at specified operating point (normal Uheater). Obviously, bias must be lowered to (green asterisk) around -3V yielding 150V/10mA plate point. But the tube doesn't seem linear enough for a line stage.

3. Gm measurements

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

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