Klausmobile Tube Tester Files

Unknown maker, 12/1985. This is visually the most beautiful tube in mini-9-pin package. The pentode's plate seems to take more space than the bottle allows, looking like a shortened EL84. All grids can be seen through the cutouts in the plate. Triode assembly, piggybacked on its side, is far smaller. The original ECF 80 was widely used in pushpull audio amplifiers (pentode as driver, DC-coupled to triode working as paraphase inverter).

1. Triode

Standard specifications per each triode
Parameter Maximum Operating Point Measured - 1989 tube
Ua, V +250 100 110
Ug, V - -2.0 -2.0
Ia, mA 14 13 12
Pa, W 1.5 (1.3) 1.3
Gm, mA/V - 5 4.9
Rp, kOhm - (4) 4.6
Mu, V/V - 20 23

1.1. Full power curve

1.2. Closeups. Note the low voltage / low current function capability before grid currents.

1.3. Gm/Mu/Rp measurements

2. Pentode - triode wiring

Recommended pentode op point is 170V plate and G2; -2.0 control grid bias; 10mA plate and 4mA G2 current. This correponds to 6.2 mA/V transonductance and gain around 1500. Of course, this is only a remote indicator of triode mode performance (although Gm should not change significantly).

2.1. Full power curve

2.2 Closeups

2.3. Gm / Mu / Rp measurements

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

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