Klausmobile Tube Tester Files

Reflector (Saratov), 12/1975. I have a treasure chest - four nearly identical 45Pi's from one production batch. How they packed 8W plate power in a mini package is a mystery, but look at the plate - it's more than 1 mm thick metal!

Standard specifications per each triode
Parameter Maximum Operating Point Measured **
Ua, V 150 150 140
Ug, V - (-1.2) -1.2
Ia, mA 52 40 33
Pa, W 7.8 (6.0) (5.2)
Gm, mA/V - 45 38
Rp, kOhm - 1.2 1.1
Mu, V/V - 52 42

** The operating point is on the edge of my gear. I shifted a bit down to get reliable readings.

The tube was a nightmare to test. It oscillated above 15mA current (at negative Ug) - despite ferrite chokes everywhere. Note that it has 2 grid leads and 4 cathode leads. I hadn't had a clue what to do with it until I looked back at specs - they require maximum gris leak resistance of 150kOhm or less. I started loading 300k resistors across grid-cathode... it took 6 (R=50kOhm) to quiet down ringing. Unfortunately, this leakage path in grid chain was not within grid amplifier loop, so the actual Ug values are 10% less than those indicated on plate curves. This also means the Gm/Mu/Rp numbers need to be re-adjusted for this Ug error, so there's no Gm/Mu tables.

Full power curve. Oddities at extreme power are caused by weak power supply, disregard them. Also disregard the color coding - this is an effect of grid leak path. Useful grid voltage is up to +0.5? before significant currents.

32mA closeup. Remember, the Ug labels must be decreased 10%.


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

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