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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

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.

  • Amiga 4000 — service manual — PDF

  • Amiga 500 — service manual PN-314981-04 (1990) — PDF

  • A1000 — PDF
  • A500 rev. 6 — PDF
  • A500+ — schematics — PDF
  • A500+ — PDF
  • A600 — PDF
  • A1200 — PDF
  • A3000 — PDF
  • A3000 (variant) — PDF
  • A4000 — PDF
  • Amiga 4000T — PDF

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.

Procedure — a dead computer, step by step ✅

What this adds

Ordered for a home computer: what kills these is its power supply, its battery, its capacitors, its socketed RAM and its keyboard — roughly in that order, and well before the CPU. → PCB diagnosis

1. The power supply — measured before it is plugged in. This is the one step not to swap around. On a machine of this age a supply does not simply stop: a 5 V regulator that fails high puts 7, 9, 12 V onto the bus and takes the RAM and the custom chips with it. Measure every rail off the machine, under a dummy load if you can, and only then plug it in. This page documents RIFA capacitors on this machine: the mains filter caps that crack, then let go in smoke on the first power-up. Replace them before you switch on, not after.

2. The battery — before anything else. This page documents a cell that leaks — check on the page whether your model is one of the affected ones, several of these pages cover a whole range. Its electrolyte eats the copper underneath and keeps eating while the machine sits in a cupboard, so it comes out first, before any diagnosis. Neutralise, clean, then check continuity on the tracks around it — a machine that no longer boots after storage is very often this and nothing else. → Backup batteries

3. Capacitors. Recap is the default on these machines, not a last resort — and on the supply first, since that is what protects everything else. → Recap

4. RAM, on its sockets. These machines were built to be repaired: the RAM, and often the logic, sit in sockets. Reseat everything first — thirty years of oxide is a classic no-boot. Then swap chips: a bad RAM chip usually gives a repeatable pattern of garbage or a screen frozen at a fixed character.

5. The keyboard. A console does not have one; a computer's is a wear part. A membrane keyboard fails as whole dead rows or columns — that is the membrane, not the machine. A mechanical one wants its contacts cleaning, not replacing. Check this page: the failure mode is often documented per model.

6. Storage — tape or disk. Both often come down to the same things: a dirty head, and for tape the azimuth and a belt turned to tar. ⚠️ On the floppy side, check whether the mechanism actually has a belt before looking for one: many do, but some drives are direct drive, and hunting a belt that isn't there means stripping a drive for nothing. A machine that boots but loads nothing is a drive fault, not a logic fault — do not go looking on the board for it.

7. Video output. RF, composite, RGB or a dedicated monitor, depending on the machine (see Identification). Test with something else before you conclude: a period modulator and a modern TV disagree far more often than either is broken.

8. Still nothing. Now the logic: rails on the board, reset, clock, bus. → PCB diagnosis

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

Sources & attribution

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.