Seawitch (Stern, 1980): faults and replacement boards (Stern M-200 MPU)
Is your Seawitch by Stern blowing fuses, failing to finish booting, showing flickering displays or playfield lamps that stay dark? These symptoms are typical of Stern microprocessor machines (M-200 MPU): the original board is now more than 45 years old and has almost always suffered from a leaking battery. A battery-free replacement board gives the machine a second life.
Seawitch (Stern, 1980): an introduction
Released in 1980, Seawitch is a Stern known for its fast playfield and its side lanes: a short, nervy game that collectors rate highly. It runs on the Stern M-200 MPU board, which is distinct from the Bally boards.
- Manufacturer: Stern Electronics
- Year: 1980
- Electronic system: Stern M-200 MPU
- Type: solid state pinball machine, 7-segment displays
- Theme: the sea, nautical fantasy
Common faults (Stern M-200 MPU)
On Stern M-200 microprocessor machines (1979-1985), the recurring faults come down to age: a leaking battery on the MPU (corroded traces around the 5101 RAM chips at U8/U13, the number one cause of dead boards), tired RAM and logic chips (no boot, reboots, looping in the tests), oxidised or burnt Molex connectors on the MPU and power supply side (pins to be replaced male and female), displays with missing or flickering segments, the rectifier and solenoid driver board (dried-out capacitors, bridge rectifier, fuses, coil transistors) and a sound board with dried-out capacitors.
Problems specific to the Seawitch (from the forums)
- The 1 A playfield fuse blowing: typically during the coil test, when the top bumper fires; check the coil and its drive transistor.
- The 10 A rectifier board fuse blowing: often goes together with playfield lamps that stay dark.
- Will not finish booting: a failing PIA (6821) on the MPU is the number one suspect reported on the forums.
- Unstable displays: a 6-digit display can throw the 7-digit displays off once it is plugged in; flickering usually comes from the wiring or the connector, not from the display itself.
- A rectifier board to go right through: the original capacitors and bridge rectifier should be replaced before any other serious work.
- High voltage reaching the MPU: causes multiple simultaneous faults; suspect it after a power supply incident.
Replacement boards compatible with the Seawitch
- BallyFA — battery-free MPU.
- BallyDri — power supply + driver.
- BallyLa_60 — lamp driver.
Plug & Play installation, battery-free, free support.
Worth knowing: the Seawitch is fitted with a Stern M-200 MPU, whose part numbers differ from the Bally -35 boards. Get in touch with the part numbers of your boards: we confirm the right solution before you buy anything.
FAQ — Seawitch Stern
Which replacement board for my Seawitch?
The Seawitch uses a Stern M-200 MPU: get in touch with the part numbers of your boards and we will confirm the right board (battery-free) before you buy.
My Seawitch is blowing a fuse — where do I start?
Identify the fuse: the 1 A playfield fuse points to a coil or its transistor, the 10 A rectifier board fuse to the power supply and the playfield lamps.
The machine powers up but never really starts.
On these Sterns, a failing PIA (6821) on the MPU is the most common case, after battery corrosion.
Should I keep the original battery?
No: a battery-free board removes the number one cause of corrosion.
What warranty comes with boards from Pinballs Store?
A 6-month warranty (parts and labour) against any fault not caused by misuse, plus 30 days money back. Technical support is free.
Does a battery-free board keep the settings and high scores?
Yes. Modern replacement boards use non-volatile memory: no battery, no corrosion, and the settings are kept when the machine is switched off.
Useful guides
- How much does pinball machine repair cost? The price guide
- How much is my pinball machine worth? Values and estimates
- Pinball machine leg sizes: the guide by machine
- Which MPU board for a Bally/Stern?
See also
Sources & further reading
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