World Defender (Nuova Bell Games, 1985): faults and replacement boards (Bally compatible)
Is your Nuova Bell Games World Defender refusing to boot, showing dead displays or runaway coils? Good news: World Defender is built on a Bally AS-2518-35 base, so the symptoms and solutions are those of Bally microprocessor machines. The BallyFA replacement MPU board, Plug & Play and battery-free, gives your machine a second life.
World Defender (Nuova Bell Games, 1985): overview
Released in 1985 by the Italian manufacturer Nuova Bell Games, World Defender reuses Bally electronics (standard Bally memory map, AS-2518-35 MPU board), with a small “rider” board carrying the ROMs on the J5 connector. Around 700 units.
- Manufacturer: Nuova Bell Games (Bally base)
- Year: 1985
- Electronic system: Bally AS-2518-35 MPU (compatible)
- Type: solid-state pinball
- Theme: defence / science fiction
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), 5101 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.
World Defender-specific issues (forum feedback)
- ROM “rider” board (J5 connector): specific to Bell Games; keep it when replacing the MPU (the ROMs also exist in standard Bally-35 format).
- 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 World Defender
- BallyFA — replacement MPU board (battery-free), Bally-35 base.
- 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 World Defender uses specific ROMs on a rider board, contact us for the right ROM configuration. Plug & Play installation, battery-free, free support. Contact us.
FAQ — World Defender Nuova Bell Games
Is the BallyFA right for World Defender?
Yes: World Defender uses a Bally AS-2518-35 base. Contact us for the configuration of the specific ROMs (J5 rider board).
My World Defender won't boot.
Check the battery and corrosion around U10/U11. The BallyFA replaces the MPU and works without a battery.
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. The BallyFA works without a battery and 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
- Powered off, visual inspection: look for any battery or corrosion marks on your World Defender's MPU, especially around U10/U11; remove the battery if it is still present.
- Power supply: measure the 5 V and check it reaches the MPU; check the bridge rectifier and the power supply fuses.
- Grounds: rework the grounds between the MPU, the power supply/driver and the display.
- Connectors: re-pin oxidised Molex connectors, especially the MPU↔power supply link.
- Displays: never plug or unplug a display while powered on; test with a known-good display.
- Final test: check boot, credits, coils and displays; the BallyFA replaces the MPU, battery-free. If needed, contact free support.
See also
- Saturn 2 (Nuova Bell Games, 1985)
- Tiger Rag (Nuova Bell Games, 1984)
- Spy Hunter (Bally, 1984)
- Kings of Steel (Bally, 1984)
