Electron tube New Automatic Computer


Ena.Computer, a tube computer for the 21st century.


Built just for the fun of doing it, with a blind faith due to my total misjudgement of the project's complexity.





With the power to both decode Lorenz traffic from 1944 and also play a mean game of pong today. The Ena.Computer is a modern 8 bit computer, with the usual 12 bit address and data buses, but the unusual current requirement of 200 Amps.


A computer that is both competent and dangerous.


After switch on you have to wait quite a while for the last electron tubes to warm up. Initially, if you look from the side you see a few start to show a red glow. After about a minute the aroma of the computer becomes the pleasant homely smell of 550 warming electron tubes burning off their dust.


When all the tubes are glowing, I check the fire extinguisher and run the code.


Ena.Computer first ran on 28th May 2021 on our dining room table, chairs and surrounding floor space.


The Final Configuration, with all the bells and whistles is now safely entrenched on the wall and is almost safe to touch.


It has been a ridiculous amount of soldering and a fantastic amount of fun.




Visiting Bletchley Park, the home of cyber warfare in Word War 2, Judy and I left the tour group and by sheer good luck met Tony Sale who with unimaginable effort rebuilt Colossus. He was running the machine at the time, and we could see in front of us the incredible work that Tommy Flowers had achieved in building Colossus during the war in 1944.

Later it occurred to me that several tube computers had been rebuilt and now run in museums, but that no new design of a tube computer had been constructed in over 50 years. The thought of building one seemed ridiculous, but I wondered if a modern design could overcome the issues of size, power and the dangers of high voltages.

When I retired I looked at the problem again and realised it could be an interesting and enjoyable endeavor.

I spent almost a year designing and building the Ena.Computer.

Unfortunately high voltages are very dangerous and shouting bang when a friend has their back to the computer is very childish, but great fun.


A Chic Heater


The Ena.Computer is designed using 1,100 thermionic triodes. Conveniently each 6N3P electron tube contains 2 triodes around a single heater, halving the physical size and power requirements.

The Ena.Computer's 550 double triode 6N3P electron tubes, are all configured as identical 5 input NOR gates. Registers and counters are built from these single NOR gates and combined into master/slave D type flip flops, an 8 bit ALU, and all latches and buffers. The amount of heat is ridiculous, but I just think of it as a trendy wall heater, then it all seems quite sensible.

The Magic


The Ena.Computer integrates eight large printed circuit boards and three auxiliary pcbs which combine the tubes into a functional computing system. The Graphical user interface, a diode matrix ROM and a reed relay RAM complete the magic to collectively become an 8 bit electron tube computer.

The Good, The Bad and The Pong Bat

Electron tubes (or just tubes in the USA) are also named thermionic valves (or just valves in the UK). The 6N3P electron tube was produced in Russia in the 1950s and is capable of switching a led on and off over 100 million times a second, which is not bad for a 70 year old.

The graphical user interface consists of a matrix of 300mw INGaN Leds.

I am attempting to write software using the GUI and its memory, combined with modern NVRAM.  Currently the Ena.Computer runs a Fibonacci Sequence.

The Ena.Computer has 8 inputs, 8 outputs plus two handshakes. A Pong bat, kinetic mouse or hex keyboard can be connected via a simple input board.

The pong bat has tilt switches in the handle which transmit basic elevation information. It is very simple and very effective.

Fibonacci Sequence Video


On 15th August 2021, three months after the first table top run with manual ALU computation and storage, the Ena.Computer is installed on a wall demonstrating a clocked, GUI displayed, Fibonacci sequence.


The Fibonacci value is displayed vertically, in binary, it requires 9 lines of code and uses both the GUI relay memory and NVRAM.