1KW Triode Push-Pull TC Driver

What do you do with a boot-load of high-power thermionic triodes?

Similar projects worth following
Flinders University in Adelaide South Australia was recently clearing out old unused components. Luckily an engineering friend spied these large vacuum tubes and I'm very pleased to say he thought of me.

Although these would look lovely on a bookshelf collecting dust, I felt they would look much better put to work and in a display to show off this early era of electronics. But what should I build? Yes, I could build an audio amplifier, but such things are commonplace, not very efficient and don't really show off their beauty and power.

So a Tesla Coil came to mind, as this would match the aesthetics and with the added benefit they are far more resilient in a harsh high voltage environment than semiconductors.

Also, rather than building a crude positive feedback oscillator on a block of wood, like many other designs on the internet. I'd design the whole thing using methods that will ensure the correct operation, have better safety and produce less RFI.

The main electronic component in this project is the 304TL thermionic triode.  A Triode is one of the first components that provided usable gain in electronics systems and so was responsible for revolutionised radio, audio and control systems in the early 20th century.  

The Triode has 3 main terminals Cathode, Grid and Anode (also called a plate). However, the cathode must be heated help liberate electrons by a filament.  In some cases, the filament will be used as the Cathode as is the case of the 304TL the heater filament is the Cathode.  The mechanical construction is usually a tube shape with the filament/cathode at the centre, then a tubular mesh around this (the Grid) and a metal tube around the outside (Anode). All this is inclosed in glass or ceramic to hold a high vacuum.

                                        The 304TL on the left has 4 Triodes wired in parallel 

When a voltage is applied across the Anode (+) and Cathode (-)  the Triode acts just like a diode allowing current to flow in one direction.  The grid is the input of the Triode and is negatively biased as the bias increases it increasingly interrupts the flow of electrons from the heated cathode to the anode similar reducing the amount of current flow, not unlike electrically to a F.E.T. 


304TL Triode Datasheet

Adobe Portable Document Format - 522.42 kB - 02/06/2021 at 04:48


View all 2 project logs

Enjoy this project?



bobu wrote 02/13/2021 at 18:22 point

It's an ambitious project.  Good luck to you.  The amplification factor of the triode is only 12.  A beam pentode (6L6G or such) might be needed to drive the grid of the Eimac triodes.

  Are you sure? yes | no

Similar Projects

Does this project spark your interest?

Become a member to follow this project and never miss any updates