Grand Slam (Bally, 1983): common faults and replacement boards (Bally MPU)
Does your Bally Grand Slam fail to boot, have dead displays or runaway coils? These symptoms are typical of microprocessor Bally pinball machines, whose original MPU board is now over 40 years old and almost always suffers from a leaked battery. The good news: the BallyFA replacement MPU board, Plug & Play and battery-free, brings your machine back to life.
Grand Slam (Bally, 1983): overview
Released in 1983 on a baseball theme, Grand Slam is a Bally pinball machine with straightforward gameplay (design by Greg Kmiec, art by Doug Watson). It uses the Bally MPU of the AS-2518 series.
- Manufacturer: Bally
- Year: 1983
- Electronic system: Bally MPU (AS-2518)
- Type: solid-state pinball
- Theme: baseball
Common faults (Bally / Stern)
On microprocessor Bally and Stern games (1977-1985), the recurring faults come from ageing: leaking battery on the MPU (corrosion of traces and sockets around U10/U11, the No. 1 cause of dead boards), tired 6821 PIAs (U10/U11) (oxidised legs, no boot), 5101 RAM and sockets to replace, MPU/power connectors oxidised or burnt (look for heat marks), displays with missing segments, and the power/driver board (rectifier, fuses, coil transistors) to rework.
Issues specific to Grand Slam (forum feedback)
- Leaked battery on the MPU: corrosion around U10/U11, to deal with first.
- Dead or partial displays: display and MPU power to check.
- Runaway or dead coils: driver board (transistors, fuses) to rework.
- Oxidised or burnt connectors: to replace (repin) for a reliable machine.
- Targets and mechanisms: outhole and target switches to clean.
- Blowing fuses: a shorted rectifier or coil to track down.
Replacement boards compatible with Grand Slam
- BallyFA — replacement MPU board (battery-free).
- BallyDri — power supply + driver.
- BallyLa_60 — lamp driver.
📚 Further reading: Guide: which MPU board for a Bally / Stern (1977-1985)?
The BallyFA replaces the original MPU board (boot-up, logic, battery-free memory) and removes the battery, the No. 1 cause of corrosion. For the coils and power, the BallyDri takes over; the lamps via the BallyLa_60. Plug & Play installation, battery-free, free support. Contact us.
FAQ — Grand Slam Bally
My Grand Slam 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 to blame: the BallyDri (power + driver) replaces it.
Is the BallyFA compatible with my Bally?
Yes, for microprocessor Bally/Stern games (1977-1985). If in doubt, contact us.
Should I keep the original battery?
No. The BallyFA works without a battery and removes the No. 1 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 the settings and high scores?
Yes. Modern replacement boards use non-volatile memory: no more battery, no more corrosion, and the settings are kept when powered off.
Step-by-step diagnosis
- Powered off, visual inspection: look for any battery or corrosion trace on your Grand Slam'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 rectifier and rework tired solder joints if the voltage drops).
- Grounds and connectors: check the grounds and repin the oxidised or burnt Molex connectors between MPU, power and driver boards.
- Key components: check the 6821 PIAs (U10/U11) and the RAM, whose sockets oxidise and prevent boot-up.
- Displays: never plug or unplug a display while powered on; test with a known-good display.
- Final test: check boot-up, credits, coils and displays; if needed, contact our free support. Reminder: the BallyFA replaces the original MPU, battery-free.
See also
- Xenon (Bally, 1980)
- Flash Gordon (Bally, 1981)
- Centaur (Bally, 1981)
- Eight Ball Deluxe (Bally, 1981)
