Polydarts Dart Machine Repair: No Schematics, No Manuals
A vintage Bulgarian electronic dart machine was stuck on a single game with zero documentation available. The fix was hidden deep inside the machine's own code.
A commercial Polydarts electronic dart machine, manufactured in Bulgaria around 2005, recently arrived at our workshop. Servicing an arcade dartboard from a niche local manufacturer is always a challenge, and this one was particularly fascinating. The machine powered on and all buttons responded with a beep, but it only offered a single game: up to 999 points in under 20 rounds, for 1 to 8 players. None of the other games were anywhere to be found.
Why was the dart machine stuck on only one game?
Our first suspicion fell on the backup battery. The machine's settings are stored in a small static RAM chip (RAM 6116), kept alive by a rechargeable battery when the machine is switched off. The original battery was dead, so we replaced it.
However, the issue persisted. We cleared the memory completely, but it still defaulted to that single game. This meant the answer had to be hidden inside the machine's firmware.
An arcade dart machine without a service manual
This is where things got tricky. The board was built by a small Bulgarian manufacturer around a 6502 CPU—a true classic from the '80s—along with three КР580ВВ55А I/O chips (Soviet clones of the Intel 8255). We searched high and low for schematics or service manuals in both Bulgarian and English, but no documentation exists anywhere.
When there are no manuals, you're left with just one source of truth: the program code burned onto the board's EPROM chip.
Dumping and analyzing the machine's firmware
Using an XGecu programmer, we dumped the contents of the EPROM chip without damaging it. We then analyzed the assembly code instruction by instruction to understand how the machine selects its games.
The findings were surprising:
The machine actually contains 16 games, none of which were locked.
The active game ID is stored in battery-backed RAM.
Due to the drained battery, that memory address held an invalid value outside the expected range, leaving the machine "stuck" on just one fallback game.
The solution itself turned out to be straightforward. Once the value was reset within the valid range, all 16 games reappeared. Without reverse-engineering the firmware, however, we would have been guessing for months. [link to: services – vintage electronics repair]
During the code analysis, we also uncovered the machine's hidden service menus, such as tournament mode and credit/counter resets—valuable information that even most owners of these machines don't have access to.
Repair or buy a new machine?
A brand-new commercial dart machine costs upwards of €2,000. Repairing the existing board brought this vintage unit back to life for a tiny fraction of that cost, restoring every single game. If your machine is older but the cabinet and circuit board are physically sound, repair is almost always the far smarter investment.
Repair of vintage arcade machines and electronics
At Maistor Zhichko, we repair electronic dartboards, arcade machines, and vintage electronics—even without schematics or documentation. When necessary, we dump and reverse-engineer the firmware. Our repair shop is located at 34 Targovska St in Gotse Delchev, Bulgaria, and we accept devices from all over the country via Econt and Speedy.
Do you have an arcade machine or vintage electronic device that isn't working properly? Send us a message or give us a call for a free consultation.
Contact us: 0886 550 529 or visit maistor-zhichko.com