Commodore Amiga¶
The 16-bit machine of gaming and the demoscene (1985-1994). A 68000 backed by a custom chipset (Agnus, Denise, Paula) doing the heavy lifting: blitter, copper, 4-channel sound, floppy DMA. For preservation, two emergencies: the leaking battery and the leaking SMD capacitors.
Amiga 500 — photo by Bill Bertram, CC BY-SA 2.5 (Wikimedia Commons).
Identification / models¶
| Model | Year | CPU | Chipset | Note |
|---|---|---|---|---|
| A1000 | 1985 | 68000 | OCS | the first, Kickstart in RAM (from disk) |
| A500 | 1987 | 68000 | OCS | the best-seller |
| A2000 / A1500 | 1987 | 68000 | OCS | desktop with Zorro slots |
| A500+ | 1991 | 68000 | ECS | ⚠️ SMD battery on the board |
| A600 | 1992 | 68000 | ECS | compact, SMD caps (leak) |
| A1200 | 1992 | 68EC020 | AGA | 32-bit, the favourite for gaming |
| A3000 | 1990 | 68030 | ECS | workstation; leaking battery |
| A4000 | 1992 | 68040/060 | AGA | high-end; battery + caps |
| CD32 | 1993 | 68EC020 | AGA | console → A1200 base |
Clocks & frequencies ✅¶
| Component | Frequency | Role / scope |
|---|---|---|
| Motorola 68000 | 7,15909 MHz (NTSC) · 7,09379 MHz (PAL) | CPU — A1000, A500, A2000, A600 |
| Motorola 68EC020 | — | A1200 (chipset AGA) |
| Motorola 68030 / 68040 / 68060 | — | A3000, A4000 et cartes accélératrices |
The 68000 frequencies are derived from the video clock, hence the NTSC/PAL difference. A PAL and an NTSC machine therefore do not run at exactly the same speed — that is normal, not a fault.
Why this matters in repair
A clock that is missing or off-value on a frequency counter points straight at the crystal, its divider chain or the component it feeds — the fastest starting point on a machine that will not boot. Source: Wikipedia (CC-BY-SA).
Architecture (the custom chipset)¶
| Chip | Role |
|---|---|
| 68000 (→ 020/030/040/060) | CPU |
| Agnus / Fat Agnus / Alice | DMA, blitter (fast copy/draw), copper (display co-processor) |
| Denise / Lisa (AGA) | video (up to HAM, 4096 colours OCS / 16.8 M AGA) |
| Paula | 4-channel sound (8-bit PWM), floppy, serial, joysticks |
| Kickstart (ROM) | the "BIOS/OS" (1.2/1.3 → 2.x → 3.x); AmigaOS/Workbench on top |
Chip RAM (chipset-accessible) vs Fast RAM (CPU only) — the split drives performance.
Repair (technician)¶
1) Leaking Varta/NiCd battery — top priority
The A500+/A600 (SMD battery), A2000/A3000/A4000 and accelerator cards have a battery that leaks and eats the board (around the clock/NVRAM). Remove it immediately, neutralise, repair the traces → see backup batteries.
2) Leaking SMD capacitors (A600, A1200, A4000)
These models' SMD electrolytics leak and corrode the board (dead sound, crashes, eaten traces) → a full recap as soon as possible, hot-air removal without ripping the pads → Recap.
- Kickstart ROM: on a socket → check version/seating; software incompatibilities per 1.3/2.x/3.x.
- DF0 floppy drive (Amiga 880 KB): tired mechanism → Gotek/HxC for preservation.
- Socketed customs (A500): diagnose by substitution (Agnus, Denise, Paula, CIA 8520 — the CIAs often fail: ports, keyboard, floppy).
- A500 PSU (external brick): check the 5 V (a tired brick causes crashes); desktop PSUs (A2000/3000/4000) have caps and mains RIFA to watch.
- Video output: 23-pin RGB → clean SCART (video mods).
Original service manual ✅¶
Manufacturer manual archived locally. It typically carries the schematics, the block diagram, the expected voltages and waveforms, the parts list and the disassembly procedures — the reference when a symptom matches no known fault.
Status
A manufacturer document with no explicit licence, kept for preservation (machine long out of production) — the same position as for the cabinet and arcade manuals already archived here. Source: Internet Archive.
Common faults¶
| Symptom | Likely cause | Lead |
|---|---|---|
| Corrosion near the clock | leaked battery | Remove, neutralise, repair traces |
| Dead sound / crashes (A600/1200) | leaked SMD caps | Recap + cleaning |
| Dead ports/keyboard/floppy | CIA 8520 | Substitute the CIA(s) |
| Won't boot | Kickstart / RAM / customs | Check ROM, substitute RAM/customs |
| Random Guru Meditation | RAM / caps / joints | RAM test, recap, reflow |
Modernisation & mods — what to buy, how¶
Reliability BEFORE anything (recap + RTC battery + PSU)
-
A600/A1200: leaking SMD caps that eat the board → a full recap is mandatory with electrolyte cleanup and a check for eaten traces before powering on.
-
A2000/A3000/A4000: a leaking Varta RTC battery → remove it urgently, repair traces, replace with lithium RTC + diode (no recharge).
-
PSU: the original bricks drift → a reliable modern regulated PSU.
Modern storage - Gotek + FlashFloppy or HxC 🟡: replace DF0/3.5″ drives (internal drive connector, set the select jumper) — ADF images from USB/SD. - A600/A1200 🟢: 44-pin IDE port → CF card as a hard disk; PCMCIA slot → CF adapter. - A500/A2000 🟠: modern SCSI/IDE controllers (trapdoor/Zorro boards) + CF/SD.
Acceleration / RAM (the big Amiga topic) - PiStorm 🟡 (Raspberry Pi on the 68000 CPU socket) = fast CPU and a virtual graphics card (RTG); otherwise TF5xx / Vampire accelerators (68080 FPGA) and RAM upgrades (A500 trapdoor, etc.).
Video - Indivision 🟠 (internal scandoubler/flicker-fixer, fits over Denise/Lisa) → crisp VGA/HDMI; otherwise RGB → SCART 🟢 then OSSC/RetroTINK or RGB2HDMI.
⚠️ Do not host Kickstart/games — method only.
See also¶
- Commodore CDTV (Amiga 500 + CD) · Backup batteries · Recap · PCB fault-finding.
Sources & attribution¶
- Photo Amiga 500 — Bill Bertram, CC BY-SA 2.5, Wikimedia Commons — https://commons.wikimedia.org/wiki/File:Amiga500_system.jpg
- Wikipedia — Amiga (OCS/ECS/AGA chipset, models, CPU) — CC-BY-SA — https://en.wikipedia.org/wiki/Amiga
- Established Amiga community knowledge (Varta leak, A600/A1200 SMD recap, CIA 8520) — synthesis.
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.
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