Cybernaut (Bally, 1985): faults and replacement boards (Bally MPU)

Is your Bally Cybernaut refusing to boot, showing dead displays or runaway coils? These symptoms are typical of Bally microprocessor pinball machines, whose original MPU board is now over 40 years old and almost always suffers from a leaking battery. Good news: the BallyFA replacement MPU board, Plug & Play and battery-free, gives your machine a second life.

Cybernaut (Bally, 1985): overview

Released in May 1985 with a science-fiction theme, Cybernaut is a rare Bally machine (around 900 units) and one of the last based on the 6800 processor. Note: it uses a logic board specific to Cybernaut (different RAM), while keeping the usual processor and the two 6821 PIAs.

• Manufacturer: Bally
• Year: 1985
• Electronic system: Bally MPU (Cybernaut-specific logic board)
• Type: solid-state pinball
• Theme: science fiction / cyborg

Common faults (Bally / Stern)

On Bally and Stern microprocessor machines (1977-1985), recurring faults come from ageing: a leaking battery on the MPU (corroded traces and sockets around U10/U11, the number one cause of dead boards), tired 6821 PIAs (U10/U11) (oxidised pins, no boot), RAM and sockets to be replaced, MPU/power connectors oxidised or burnt (look for heat marks), displays with missing segments, and the power supply/driver board (rectifier, fuses, coil transistors) needing rework.

Cybernaut-specific issues (forum feedback)

• Machine-specific logic board: Cybernaut uses a unique MPU (RAM different from the standard 5101); contact us to confirm the right replacement solution.
• Leaking battery on the MPU: corrosion around U10/U11.
• Dead or partial displays: check the display and MPU power supply.
• Runaway or dead coils: rework the driver board (transistors, fuses).
• Oxidised or burnt connectors: replace (re-pin) them to make the machine reliable.
• Blowing fuses: look for a shorted rectifier or coil.

Replacement boards compatible with Cybernaut

• BallyFA — replacement MPU board (battery-free).
• BallyDri — power supply + driver.
• BallyLa_60 — lamp driver.

📚 To go further: Guide: which MPU board for a Bally / Stern (1977-1985)?

The BallyFA replaces the original MPU board (boot, logic, battery-free memory) and removes the battery, the number one cause of corrosion. As Cybernaut uses a machine-specific logic board, contact us to confirm compatibility before ordering. For coils and power, the BallyDri takes over; for lamps, the BallyLa_60. Plug & Play installation, battery-free, free support. Contact us.

FAQ — Cybernaut Bally

Is the BallyFA right for my Cybernaut?
Cybernaut has a machine-specific logic board; contact us with your board references to confirm the right solution.

My Cybernaut won't boot.
Check the battery and corrosion around U10/U11. The battery is the number one cause of dead boards.

Some coils run away or don't respond.
On the power side, the driver board is at fault: the BallyDri (power supply + driver) replaces it.

Should I keep the original battery?
No. A battery-free replacement board removes the number one cause of corrosion.

How long does it take to install a replacement board?
Installation is Plug & Play: a few minutes, no soldering, with tutorials and free support.

Does a battery-free board keep settings and high scores?
Yes. Modern replacement boards use non-volatile memory: no battery, no corrosion, and settings are kept when powered off.

Step-by-step diagnosis

1. Powered off, visual inspection: look for any battery or corrosion marks on your Cybernaut's MPU, especially around U10/U11; remove the battery if it is still present.
2. Power supply: measure the 5 V and check it reaches the MPU (check the rectifier and rework tired solder joints if the voltage drops).
3. Grounds and connectors: check the grounds and re-pin oxidised or burnt Molex connectors between MPU, power supply and driver.
4. Key components: check the 6821 PIAs (U10/U11) and Cybernaut's specific RAM, whose sockets oxidise and prevent booting.
5. Displays: never plug or unplug a display while powered on; test with a known-good display.
6. Final test: check boot, credits, coils and displays; if needed, contact free support. Reminder: Cybernaut's logic board is machine-specific, so confirm compatibility before replacing.

See also

• Xenon (Bally, 1980)
• Flash Gordon (Bally, 1981)
• Centaur (Bally, 1981)
• Eight Ball Deluxe (Bally, 1981)

Sources & further reading

• Pinside forum — Cybernaut
• IPDB — Cybernaut (#614)
• OPDB — Open Pinball Database