Sega G80 (raster & vector)¶
Sega's flexible early-80s platform (1981), in two versions: raster (Astro Blaster, 005, Monster Bash) and vector (Space Fury, Star Trek, Eliminator, Tac/Scan, Zektor). The vector side shares the constraints of Atari's vector cabinets: an XY monitor and high voltage.
Identification¶
| Field | Value |
|---|---|
| Manufacturer | Sega / Gremlin |
| Years | 1981-1983 |
| Versions | G80 raster · G80 vector |
| CPU | Zilog Z80 |
| Sound | dedicated sound boards + speech synthesis depending on the game |
Architecture¶
| Block | Chip | Role |
|---|---|---|
| CPU | Zilog Z80 | game logic |
| Video (raster) | tiles + sprites | Astro Blaster, 005, Space Odyssey, Monster Bash, Pig Newton |
| Video (vector) | vector generator + XY monitor | Space Fury, Zektor, Tac/Scan, Eliminator, Star Trek: SOS |
| Sound | Universal Sound Board + per-game speech/sound boards | music/SFX + synthesized speech (Space Fury, Star Trek…) |
⚠️ Zaxxon is NOT a G80 game: despite Sega's "Convert-a-Game" promise, the big hits Zaxxon and Pengo shipped on bespoke hardware — Zaxxon's success actually undermined the G80 concept. The last G80 came in 1983.
The vector side (specific repair)¶
Vector G80s use an XY monitor (often Electrohome G08), with the same dangers as the Atari vector:
- CRT high voltage → discharge before working on it.
- Fixed bright dot = phosphor burn risk → cut power immediately.
- Repair = recap + reflow of the deflection, vector-generator diagnosis.
Notable games¶
- Raster: Astro Blaster (1981), 005, Space Odyssey, Monster Bash.
- Vector: Space Fury (1981), Zektor, Tac/Scan, Eliminator, Star Trek: Strategic Operations Simulator (1982, the most famous).
Common faults¶
| Symptom | Likely cause | Lead |
|---|---|---|
| Distorted/missing lines (vector) | XY deflection / joints | Reflow, deflection diagnosis |
| Dead screen, HV ok (vector) | vector generator / caps | Recap + diagnosis |
| No speech (SFX ok) | speech board | Speech-board diagnosis |
| Corrupt raster image | video RAM, Z80 | RAM test, contacts |
| No image | Power, Z80, harness | Base diagnosis |
Modernisation & mods¶
The common ground for every JAMMA board
Video, power, control panel and upscalers depend on the cabinet rather than the board: everything is centralised in Modernising a cabinet. To run the board outside a cabinet (at home, on a display): supergun.
- Storage 🟡: the game lives in EPROM/mask ROM on the board. Changing or restoring a game means reprogramming the EPROMs (and, for a mask ROM, using a pinout adapter) → EPROM method.
- Media preservation: replacing the original storage, multicarts, ODEs and modern options by family → PCB preservation hub.
- Scan rate 📺: ~15.72 kHz / 60.0 Hz (raster versions) — standard resolution, a classic 15 kHz chassis is fine → tri-sync and upscalers.
(Computed from the MAME sources —
sega/segag80r.cpp— pixel clock ÷ htotal.) - FPGA / emulation: see the Emulation & FPGA section below.
Repair (technician)¶
- Sega 315-xxxx encryption (address/data) on many games: without the correct decode board/chip the game won't run — check before suspecting the logic.
- Vector side: a high-voltage XY monitor → CRT safety.
- Speech: a separate voice synthesis board — silent voice ≠ a main-sound fault.
- Discrete Z80 logic: TTL/RAM/buffer diagnosis; 2716/2732 EPROMs on sockets (oxidised legs → turned-pin socket).
→ Methods: PCB fault-finding · Recap · EPROM · Traces & vias
Expected clocks — measurement table ✅¶
Values extracted from the MAME sources for this platform. On a scope or frequency counter, a clock that is missing or off-value points straight at the crystal, the divider or the chip at fault — the fastest starting point on a dead board.
| Component | Expected clock | Role |
|---|---|---|
| Z80 | 3.86712 MHz · 4 MHz | sound CPU (usually) |
How to read this table
Several values for one component = several board variants in this family (or several instances of the chip clocked differently). These frequencies are those of the clock signal at the component's input, not of its original crystal — on many boards the clock is divided down from a single master crystal.
Archived original schematics ✅¶
Manufacturer schematics for games in this family, archived locally. They give the clock tree, the address decoding and the breakdown of the video/sound/power stages — enough to trace a missing signal back to its source.
- Highway (TM-028) — full schematic (PDF)
- Monster Bash — full schematic (PDF)
- Tranquilizer Gun — full schematic (PDF)
Scope
A schematic applies to the game and revision named: within a family the general breakdown carries over, but component references and custom chip pinouts do not transpose. Source: the Arcade Game Manuals collection (Internet Archive), manufacturer documents kept for preservation.
Manufacturer service bulletins ✅¶
Fixes the manufacturer issued to its network: they document a factory-acknowledged fault, its symptom and the modification to apply.
→ Full catalogue: service manuals & wiring diagrams
DIP settings ✅¶
8 games on this platform, settings extracted from the MAME sources (INPUT_PORTS_START blocks). The Position column gives the switch's physical reference on the board (SW2:!3,!4 = bank SW2, levers 3 and 4) — which is what lets you set it up without the paper manual. Games are sorted by MAME set name.
DIP settings — MAME set 005
| Setting | Position | Options (default in bold) |
|---|---|---|
| Lives | SW1:8,7 | 3 · 4 · 5 · 6 |
| Cabinet | SW1:6 | Upright · Cocktail |
DIP settings — MAME set astrob
| Setting | Position | Options (default in bold) |
|---|---|---|
| Lives | SW1:8,7 | 2 · 3 · 4 · 5 |
| Cabinet | SW1:6 | Upright · Cocktail |
| Demo Speech | SW1:5 | Off · On |
DIP settings — MAME set astrob2
| Setting | Position | Options (default in bold) |
|---|---|---|
| Lives | SW1:8,7 | 2 · 3 |
DIP settings — MAME set g80r_generic
| Setting | Position | Options (default in bold) |
|---|---|---|
| Coin A | SW2:8,7,6,5 | 4C 1C · 3C 1C · 2C 1C · 2 Coins/1 Credit 5/3 6/4 · 2 Coins/1 Credit 4/3 · 1C 1C · 1 Coin/1 Credit 5/6 · 1 Coin/1 Credit 4/5 · 1 Coin/1 Credit 2/3 · 1C 2C … |
| Coin B | SW2:4,3,2,1 | 4C 1C · 3C 1C · 2C 1C · 2 Coins/1 Credit 5/3 6/4 · 2 Coins/1 Credit 4/3 · 1C 1C · 1 Coin/1 Credit 5/6 · 1 Coin/1 Credit 4/5 · 1 Coin/1 Credit 2/3 · 1C 2C … |
DIP settings — MAME set monsterb
| Setting | Position | Options (default in bold) |
|---|---|---|
| Lives | SW1:8,7 | 3 · 4 · 5 · 6 |
| Cabinet | SW1:6 | Upright · Cocktail |
| Difficulty | SW1:5,4 | Easy · Medium · Hard · Hardest |
| Bonus Life | SW1:3,2 | 10000 · 20000 · 40000 · None |
| Infinite Lives (Cheat) | SW1:1 | Off · On |
DIP settings — MAME set pignewt
| Setting | Position | Options (default in bold) |
|---|---|---|
| Cabinet | SW1:8 | Upright · Cocktail |
| Demo Sounds | SW1:7 | Off · On |
| Lives | SW1:6,5 | 3 · 4 · 5 · 6 |
DIP settings — MAME set sindbadm
| Setting | Position | Options (default in bold) |
|---|---|---|
| Lives | SW1:8,7 | 3 · 4 · 5 · 6 |
| Cabinet | SW1:6 | Upright · Cocktail |
| Infinite Lives (Cheat) | SW1:1 | Off · On |
| Coin A | SW2:8,7,6,5 | 4C 1C · 3C 1C · 2C 1C · 2 Coins/1 Credit 5/3 · 2 Coins/1 Credit 4/3 · 1C 1C · 1 Coin/1 Credit 5/6 · 1 Coin/1 Credit 4/5 · 1 Coin/1 Credit 2/3 · 2C 3C … |
| Coin B | SW2:4,3,2,1 | 4C 1C · 3C 1C · 2C 1C · 2 Coins/1 Credit 5/3 · 2 Coins/1 Credit 4/3 · 1C 1C · 1 Coin/1 Credit 5/6 · 1 Coin/1 Credit 4/5 · 1 Coin/1 Credit 2/3 · 2C 3C … |
DIP settings — MAME set spaceod
| Setting | Position | Options (default in bold) |
|---|---|---|
| Lives | SW1:8,7 | 3 · 4 · 5 · 6 |
| Cabinet | SW1:6 | Upright · Cocktail |
| Bonus Life | SW1:5,4 | 20000 · 40000 · 60000 · 80000 |
| Infinite Lives (Cheat) | SW1:1 | Off · On |
Check against your own board
These settings apply to the game and revision described by MAME. One title may have several DIP sets depending on region or revision, and some systems use soft-dips (settings in memory, via the test menu) rather than physical switches. In case of a discrepancy, the board's silkscreen and the test menu are authoritative.
See also: DIP reference · game manuals
Emulation & FPGA¶
- Emulation: MAME (
sega/segag80r.cpp,sega/segag80v.cpp). - FPGA / MiSTer: no confirmed dedicated G80 core → MAME.
EPROM repair¶
Z80 program: raster (Zaxxon, Congo Bongo) / vector (Space Fury, Star Trek, Tac/Scan). 2716 / 2732 EPROMs. ⚠ Many use a Sega address/data encryption (315-xxxx) → decode board required.
Lineage¶
Contemporary with Sega arcade's beginnings; precedes the System 1 (1983). Vector kinship with the Atari vector.
Photos / assets¶
(To add: G80 card cage, vector generator, Electrohome G08 XY monitor.)
Sources & attribution¶
- Sega Retro — Sega G80 (raster + vector, Z80, games, sound/speech boards) — https://www.segaretro.org/Sega_G80
- System16 — Sega G80 Vector Hardware — https://www.system16.com/hardware.php?id=686
- MAME —
sega/segag80r.cpp&sega/segag80v.cpp— https://github.com/mamedev/mame
Review & corrections
How this space is used
Spotted a wrong value, an outdated procedure, a chip reference that does not match your board? Say so here, with what you observed (model, board revision, serial number, measurement). Every report is cross-checked against a source before anything changes — an unverifiable correction is published as “reported by …, not cross-checked” rather than silently applied.
Reading is open to everyone; posting requires signing in with Discord. Reports from the wiki's declared reviewers are handled first; anyone else's are read too, but go through a human before anything is changed.