Mr. Contact's Ena.Computer Is a Modern, Miniature Vacuum Tube Computer — and It Plays Pong

A pseudonymous retired engineer known as "Contact@Ena.Computer" or "Mr. Contact" has been working on a homebrew computer with a difference: It's made using vacuum tubes, in a throwback to the era of systems like ENIAC and Colossus.

"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," Mr. Contact explains of the origins of his project, the Electron-tube New Automatic Computer or Ena.Computer. "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."

The concept was shelved through a lack of time, until retirement. "When I retired I looked at the problem again and realised it could be an interesting and enjoyable endeavour. I spent almost a year designing and building the Ena.Computer. Unfortunately 300 volts is very dangerous and shouting 'bang' when a friend has their back to the computer is very childish, but great fun."

The finished system, which was only recently completed and transferred from surfaces around the house to an attractive wall-mount display, is built around 550 double triode 6N3P electron-tubes configured as five-input NOR gates — bulky, power-hungry devices which served as the heart of electronic computers until the invention of the transistor relegated them to selected Hi-Fi and radio equipment.

"Registers and counters are built from these single NOR gates and combined into master/slave D-type flip flops, an eight-bit ALU [Arithmetic and Logic Unit], and all latches and buffers," Mr. Contact explains. "The amount of heat is ridiculous, but I just think of it as a trendy wall heater, then it all seems quite sensible."

"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 eight-bit electron tube computer."

That GUI is a far cry from a modern high-resolution monitor, too: it's a simple matrix of LEDs, for which Mr. Contact is in the process of writing a clone of Atari's classic Pong. To further that project, he has also developed a racquet with tilt switches in the handle — acting as a third input device alongside a hexadecimal keyboard and a kinetic mouse.

"I could not find any translations for non-technical enquiries into English, so I offer my own," Mr. Contact notes with tongue firmly in cheek. "'What's it do?' means 'I'm bored.' 'Why did you build it?' means 'I'm really bored.' 'Should it spark like that?' means. 'I'm really scared.'

Full details on the project can be found on the Ena.Computer website.