Tog Hackerspace

Not every evening in Tog involves waking up a piece of 1980s Eastern Bloc computing, but that is exactly what happened over a few nights recently.

Our member Eduard Garanskij brought in a retro CRT terminal, a Mera CM 7209, also known as the MERA 7953 Z. It is a computer terminal rather than a full computer, the sort of screen and keyboard setup that would have connected to larger systems. The CM 7209 name was used for the international market, while MERA 7953 was the Polish domestic name. These terminals were made in the 1980s by Mera-Elzab in Zabrze, Poland. Read more on Wikipedia.

Mera-Elzab was part of Poland’s computing industry and produced terminals, monitors and computers. In the 1980s it was counted among Poland’s major industrial enterprises and exporters. Mera-Elzab also produced the Meritum computer family.

The CM 7209 was designed to work with systems such as SM-series computers and PDP-11-compatible machines. It is functionally close to a DEC VT52-style terminal, showing rows of green text on a CRT display. That gives it a lovely place in computer history, somewhere between mainframe rooms, minicomputers and the world before personal computers became common. You can fall down that rabbit hole with PDP-11 and VT52.

Of course, “new retro computer” usually means “new set of problems to solve”. The terminal still needs more work, but the first job was to find out if the CRT was alive. With help from Ambrose, Garry and Roman, Eduard opened it up, checked around the boards, traced signals and carefully brought it back to the point where the screen lit up.

And then, the magic moment: green glow.

It is hard to explain to normal people why a screen full of messy green lines can make a room full of hackers happy, but it does. It means there is life in there. It means the tube is working. It means the next stage of the repair can begin.

A nice bonus discovery was inside the machine: some of the chips were stamped Made in Ireland. There is something lovely and strange about that. A Polish terminal, from the Eastern Bloc era, designed to talk to Soviet-compatible computer systems, now sitting on a bench in a Dublin hackerspace, with Irish-made silicon inside it. We talk a lot about living in a connected world, but apparently, the connected world was already there. It just weighed more and had a CRT.

Eduard also noted that similar Mera CM 7209 terminals have appeared in photos connected with Pripyat and Chornobyl-era sites, which adds another layer of Cold War computing history to the story. We will leave the full Chornobyl rabbit hole for another night, but it is a reminder that these machines were not just office furniture. They were part of real industrial and scientific systems.

The terminal is not fully fixed yet, but that is part of the fun. Retro repair is rarely one clean “before and after” moment. It is usually a few evenings of poking, testing, asking someone across the room to have a look, and celebrating each tiny bit of progress.

Huge thanks to Eduard for bringing it in and sharing the story, and to Ambrose, Garry and Roman for helping to light up the screen.

If you are into retro computing, electronics repair, old keyboards, mystery connectors or the warm green glow of a CRT, drop into one of our open nights. You never know what will arrive on the bench next.

Safety note: CRTs can hold dangerous voltages, even when unplugged. This is one for careful repair with people who know what they are doing.