Nugent (Stern, 1978): faults and replacement board (Stern M-100 MPU)
Is your Stern Nugent refusing to start, completely silent, producing a continuous hum from the speaker or showing dead displays? These symptoms are typical of Stern microprocessor pinballs (M-100 MPU): the original board is over 45 years old and almost always suffers from a leaking battery. A battery-free replacement board gives the machine a second life.
About the Nugent (Stern, 1978)
Released in November 1978 on a rock theme built around Ted Nugent, Nugent is a solid-state pinball from Stern Electronics designed by Mike Kubin, with roughly 2,873 units produced. Its backglass reuses the artwork from the Weekend Warriors album (1978). The playfield offers two banks of drop targets, a spinner, a bonus saucer, pop bumpers and a free ball return lane. It uses the Stern M-100 MPU board and the SB-100 sound board.
- Manufacturer: Stern Electronics
- Year: 1978
- Electronic system: Stern M-100 MPU (+ SB-100 sound board)
- Type: solid-state pinball
- Theme: rock / music (Ted Nugent)
Common faults (Stern M-100)
On Stern M-100 machines (1977-1979), the recurring faults all come from ageing: a battery leaking on the MPU (corroded traces around U10/U11, the number-one cause of dead boards), tired logic circuits (5101 RAM, 6821 PIA, no boot possible), oxidised or burnt Molex connectors between the MPU and the power supply, displays with missing segments, and the power/driver board to overhaul (bridge rectifier, fuses, coil transistors).
Nugent-specific issues (from forums)
- Loud speaker hum from the moment you power up, often after a re-pinning job: redo the connectors at the SB-100 end as well as at the far end of the link.
- No sound at all: on the SB-100, a failing U17 (LM324) or U9 (4013) blocks the multivibrator.
- Sound board will not start: the J5 connector is easy to seat one pin out of line; check its alignment before anything else.
- Sound restored after replacing the MC3340 (electronic volume control): a frequently reported fix.
- Battery leaked on the MPU: deal with this first — the corrosion attacks the traces under the U10/U11 sockets.
- Patchy documentation: Stern manuals do not list sound board components the way Bally manuals do, which makes diagnosis harder.
Replacement boards compatible with the Nugent
Important: the Nugent uses a Stern M-100 MPU, close to but distinct from the Bally boards. Confirm the right board before ordering: contact us with the references of your boards.
- BallyFA — battery-free MPU.
- BallyDri — power supply + driver.
- BallyLa_60 — lamp driver.
Plug & Play installation, battery-free, free support.
FAQ — Nugent Stern
Which replacement board for my Nugent?
The Nugent is fitted with a Stern M-100 MPU: contact us with the references of your boards and we will confirm the right solution (battery-free).
My Nugent hums constantly through the speaker.
That drone almost always comes from a badly re-pinned connector on the SB-100 link; check both ends before suspecting the board itself.
My Nugent has no sound at all.
On the SB-100, test U17 (LM324), U9 (4013) and the MC3340: those three are the most frequent culprits.
Should I keep the original battery?
No: a battery-free board removes the number-one cause of corrosion.
Does a battery-free board keep the settings and high scores?
Yes: non-volatile memory keeps settings and scores when the machine is switched off, with no battery and no corrosion.
What is the warranty?
6-month warranty (parts and labour) against any fault not caused by misuse, plus 30 days money-back. Free technical support.
See also
Sources
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