• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Was ist das?

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What sort of tube is this ?


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I can't make out a lot of the internals but it looks like it has beam forming plates, so probably a tetrode. From the size and shape withthe top cap fpr the plate, I'd venture that it is made for high voltage >600V.

Power transmitter tube for HF maybe.

Might be suitable for output tube, might not.

No numbers on the tube or box?
I recall venturing across a webpage about gigantic tubes, it was on one of those german websites, either Jogi's Roehrenbude or Burkhard Kainka's website I believe (I'm too lazy to check :p ).

The article was about one of those gigantic Kriegsmarine WW2 or thereabouts era tubes, it looked awesome, almost exactly like the one pictured but IIRC it had two glass protrusions rather than one (so not just anode but also access to another electrode via bulb rather than underlying socket pins).
Wow! That tube is bigger than I thought. From the first picture I figured it was about 5" tall and 2-1/2" in diameter. I bet it is more like 10" tall and 6" in diameter.

You can get 40Ma at 30KV out of a Neon Sign Transformer, but I sure don't want to try working with it.

175W in heater supply alone means it will be a real power hog.
Looks like you nailed it! Thank You.

With your input and a bit of googling I think I now know what it is - a GMI-90 Beam Tetrode in its Socket.

More pics here: 4hv.org: Forums / Projects / GMI-90 Project ideas

This tubes Russian (GMI family) is incredible `Beast`,have huge cathode surfaces beacose is intendet for high voltage Pulse operation(Magnetron Tube Pulse Modulator)(Up to 150KV B+) and if You look good that tube datasheet output power in that pulse operation mode is Huge too.Pitty, in that datasheet You can always found only value for RADAR modulator purpose,nothing else, but that tube is quit good for high power Audio Amps,Radio transmitter,even for OTL Amps(conected triode).Any way if You want to implement this tube somewhere,watch out this:When You cross 12KV anode voltage they start to produce and emit X-Ray, so some kind of protection You must considere.All the best
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