• 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.

A mystery device

Guess, what it is?


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For starters I will expose some theory: All tube operation is the fact that any metal is continuously emitting electrons. The speed with which they are emitted increases very strongly with temperature, although in fact emission takes place at anything above absolute zero. To understood emission, we have to look at what is going on inside the body of the metal. In any metal, there are one or two electrons that can easily be detached from an atom. The latter are fixed in place inside the crystal structure and do not move about at all, although they vibrate in place.Since the electrons are not attached to any particular atom, they move about constantly, very much like the molecules in a gas. The average speed of the electrons increases with temperature, but because they are constantly bouncing off of the atoms and each other they do not all have the same speed but rather obey a statistical distribution law. If an electron happens to be going towards the surface of the metal, then it will naturally tend to fly right out through the surface. When an energetic, fast-moving electron hits a metal surface, the impact dislodges some of the other electrons and causes them to be emitted.

For example:
An electron arriving at a 250V plate has an energy of 250eV, whereas the metal’s work function means that only around 4eV is required for an electron to be emitted. This phenomenon is called secondary emission and occurs each and every time an energetic electron arrives.

One of the main problems in the functioning valve tubes is secondary emission, in other words, secondary current flow, is almost never a good thing. The cathode tube is a conductor and therefore has a Fermi energy (Ef) in its conduction band. I think in that diagram, this Ef energy is plotted.


2009-04-08 11:12 pm
Some new linear tube amp you've cooked up?
If its just measurements off of one tube id like to get my hands on it that graph shows it being operational with 23v@0.06ma. looks like a good candidate for a low power amp or tube front end for a transistor amp.

-edit- nvm i feel like a dummy now i didnt see that there were 5 harmonics there.
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Guess, what it is? ........Looks like some typical sweep tube curves with positive g1 voltages.

It would be a really bad sweep tube if the current only gets to 1 ma with hundreds of volts across the tube.

Unless Wavebourne is screwing with us by changing the names of the terms it looks like the variable here (Vf) is filament voltage. If it can drop 300 volts at 1mA in normal operation without complaints from the user it must operate at a high voltage. My guess is a HV rectifier tube from a TV set. Something like a 1B3 or 3A3 or if we believe the Vf curves a 2X2.


2006-07-27 11:45 pm
Similar to a GE10/CV5109, a saturated diode? The GE10/CV5109 data sheet has a graph very similar to the one that was posted in the first post.

Didn't Sch3mat1c identify it as such in post #3?

From GE10 / CV5109 : "This is a directly heated tungsten filament diode intended for operation with temperature limited emission. The large change in anode current resulting from a small change in filament voltage together with the stability of the valve make it suitable for use as a control in stabiliser circuits."

As for its purpose, I don't know for sure but I’d guess that it could be used to derive a control signal used to stabilize B+ against variations in heater supply????
drj759 won!

Actually, it is a 2AS15A diode that was used in voltage regulators of measurement instruments. It sensed filament voltage and controlled power tube's grid voltage; power tube controlled magnetic amplifier (like a choke with additional winding to control saturation) to control primary voltage on the transformer. As the result, all voltages were stabilized.

A nice simple regulated current source, huh?