Are there purely diode, vacuum tubes?

Any diode such as 6AL5. Or maybe use a triode and connect the grid to anode. Then 6C4 or 6J5 would be suitable.

 

The 1B3GT Half-Wave Rectifier.

 

why this requirement ... considering most are such ?

well if it has a grid, it isn't a diode ! at minimum it's a triode


Dave

 

a slightly rough way to do it, specially when there are many purpose built rectifiers out there

eg what Don has shown or here's another one



The 5U4G is a twin diode, use one or use both sections, take your pick



Dave

 

There are so many thermionic diodes to choose from. What is the application?
What is maximum reverse voltage and current? What is maximum forward current?
What frequency? and maximum capacitance between anode and cathode?

 

Am I the only one who finds the above quotes by the same person a bit odd?

 

Ummm, well in the first post it seems very important that the plate completely surrounds the cathode. In the other post I quoted it looks as if you were not even sure that tubes are actually constructed in that manner.

 

You can find all the answers to you questions in the RCA Tube Manual which you can download for free here. http://www.tubebooks.org/tubedata/RC30.pdf
Page five will give a general understand of vacuum tube diodes which are used as rectifiers.

Pretty much anyone who is experimenting with vacuum tubes will be using this manual. There will be more than a quick glance needed to understand this subject so you should expect to spend a good amount of time to get to understand what you read. As tube diodes are the least complex of the vacuum tubes, tube diodes will be not too hard too understand.

If you get stuck and need help, post here or PM me.

Cheers,

Billy

 

because of the big potential difference between the plate ( anode) and the filament (cathode)

totally different situation, doesn't relate to what is happening in a tube


Dave

 

Probably. It is an external electrostatic screen or metal envelope. The plate or anode is, a.

The cylindrical plate structure is connected to a small top cap, well away and isolated from the pins, marked as p on the diagram. The black bump at the bottom of the diagram is a locating index on the base socket.


The slender filament heated cathode is mounted on a central axis. The tubular anode plate surrounds the cathode, so the heat due to the accelerated electrons impacting the inside of the anode, can be radiated from the larger area of the tubular anode, outwards through the glass envelope.
Electric fields close to the cathode are critical to electron emission. For a triode, the control grid is placed very close to the cathode. The fields inside a capacitor or coaxial cable are all internal, similarly, the electric fields between the cathode and the inside of the tubular anode of a vacuum tube are self-screened which reduces the effects of external electric noise and so reduces interference with other nearby components and signals.
It was Lee DeForest who first investigated the triode amplifier. He discovered the effect when placing an antenna wire against the outside of the glass envelope of a thermionic diode that was being used as a wireless signal detector. It became his “Audion” in 1905.
It is lucky he was not using a tubular anode electrode, but something more resembling the separated anode “plate” still used in tube diagrams.

 

if the plate is negative, then the electrons from the filament (cathode) will be repelled and the tube wont work

 

not sure
I see absolutely no point in doing that ??

 

Samson4,

Any DC current coming from a tube diode will need filtering the same as would be the case with a silicon diode. All that comes out of a tube diode is pulsating DC. Connecting up a tube in a non standard way will most like destroy the tube and perhaps blow up in you face, set the house on fire....well...those are the minor issues that could come to pass...lol

Most tubes are high voltage devices, connected from the mains by a step up transformer designed to provide the correct voltage needed by the tube. Nothing about this is simple or cheep and has the real danger of getting you killed if you mess something up.

Please proceed with due caution if you go forward with this sort of stuff.

Cheers,

Billy

 

Quiet electrically or acoustically? Audio noise is usually generated by physical movement in magnetic components. Magnetostriction in a magnetic core or movement of windings on the core can often be a problem.

EHT flyback rectifiers are often made from chains of diodes with parallel resistors to equilibrate the reverse voltages across the many diodes. They are called “stick rectifiers”. The 1B3GT shown by dlgoff in post #3 was designed for use in EHT generators for B&W TV. It was replaced by semiconductor stick rectifiers.
Flyback diodes often need snubber networks made from series connected R and C. Snubbers restrict dv/dt and prevent voltage spikes that may damage semiconductor components or insulation.

Avoid the word “screen” as that refers to an internal grid close to the plate. The black circle, M, in the diagram is not strictly an electrode. It may be a metal sleeve inside and/or outside the vacuum envelope.

I think you are trying to use an inappropriate component do something you have not clearly specified. If you knew more about thermionic vacuum tubes you might see better ways of resolving your design requirements. It is highly unlikely that you will find neat low cost technical solutions by random assemblages of components you do not yet understand.

There is a wealth of knowledge available from the members of PF. If you specify your project and the problems you are having, you will receive several good suggestions from members, probably along with a better understanding of your design challenge. If you could ask the right question, you could answer it yourself. When you explain a project or problem to others, you will actually get to understand it better yourself. Give it a try here.

 

Surface leakage across the glass base, or voltage breakdown between the pins will severely limit the voltages possible.

 

Connect d1 and d2 to m, ground k1 and k2, heat the filament. Some electrons will be emitted from the heated k, to reach d and so drive it negative. That will repel future electron migration and so limit the voltage.

How will you use 19V to pump charge onto the capacitance of the outer mesh ?
Remember that the filaments should be operated at a similar voltage to the k voltage.
What makes the vacuum tube better than a tin can ?