Amiga Machine Hub
A500, A600 & A1200 repair reference — SMD recapping, video output, diagnostics and connector pinouts for the workbench.
Model Selector
Select your Amiga model to view board details, key ICs, and recap specifics.
Amiga 500 Rev 3 – Rev 8A • 1987–92
The best-selling Amiga model. Uses through-hole electrolytic capacitors (no SMD cap leakage risk on most revisions). OCS chipset with 512 KB Chip RAM on-board, expandable to 1 MB via trapdoor. DB23 RGB video output at 15 kHz PAL/NTSC. The Rev 5 and later boards added the "Fatter" Agnus (8375) supporting 1 MB Chip RAM natively.
Key ICs
- CPU: Motorola 68000 @ 7.09 MHz (PAL)
- Agnus: 8371 (Fat) / 8375 (Fatter) — DMA controller, blitter, copper
- Denise: 8362 — video output & sprites
- Paula: 8364 — audio (4 channels) & floppy/serial I/O
- CIA ×2: MOS 8520 — keyboard, joystick ports, TOD clock
- Gary: Gate array — address decode & bus arbitration
- Kickstart ROM: 256 KB (1.2 / 1.3 / 3.1)
Electrolytic Capacitor Recap Notes
Most A500 boards use through-hole radial electrolytics. These are far less prone to leakage than SMD caps, but should still be replaced after 30+ years as ESR increases and capacitance drops.
| Area | Typical Values | Notes |
|---|---|---|
| Main filter | 1000 µF 16 V, 470 µF 16 V | 5 V rail bulk filtering |
| Audio path | 10 µF 16 V ×4 | Coupling caps near Paula; affects audio quality |
| Video | 47 µF 16 V, 10 µF 16 V | RGB output filter & composite encoder |
| Floppy | 10 µF 16 V | Drive controller decoupling |
| Keyboard | 22 µF 16 V, 47 µF 16 V | Keyboard controller filter |
Replace with 105 °C low-ESR electrolytics. No SMD cleanup needed on standard A500 boards.
Amiga 600 Rev 1.5 – Rev 2B • 1992
Compact ECS-based Amiga with SMD surface-mount construction. Highly susceptible to SMD capacitor leakage — leaking electrolyte corrodes traces, vias, and pads. Ships with 1 MB Chip RAM, PCMCIA slot, and 2.5 " IDE header for hard drive. No numeric keypad. DB23 RGB output at 15 kHz.
Key ICs
- CPU: Motorola 68000 @ 7.09 MHz (PAL)
- Agnus: 8375 (Fatter Agnus) — 1 MB Chip RAM support
- Denise: 8373 (Super Denise / HiRes Denise) — ECS enhancements
- Paula: 8364 — audio & I/O
- CIA ×2: MOS 8520
- Gayle: Gate array — IDE, PCMCIA, interrupt logic
- Budgie: (on some revisions) — bus buffer
- Kickstart ROM: 512 KB (2.05 / 3.1)
SMD Capacitor List (Critical Recap)
The A600 uses SMD electrolytics that leak corrosive electrolyte. Recap is essential — even machines that appear to work will have leakage in progress. See the corrosion cleanup guide below.
| Ref | Value | Voltage | Area / Notes |
|---|---|---|---|
| C401 | 100 µF | 6.3 V | Audio filter |
| C402 | 100 µF | 6.3 V | Audio filter |
| C403 | 22 µF | 16 V | Audio coupling |
| C404 | 22 µF | 16 V | Audio coupling |
| C405 | 10 µF | 16 V | Keyboard controller |
| C811 | 47 µF | 16 V | 5 V rail filter |
| C812 | 47 µF | 16 V | 5 V rail filter |
| C813 | 100 µF | 10 V | Main filter (near fuse) |
| C821 | 47 µF | 16 V | +12 V rail |
| C822 | 47 µF | 16 V | -12 V rail (audio bias) |
Tip: Replace all SMD electrolytics with polymer or tantalum SMD caps (same footprint). Check for corroded vias under and around every cap pad — use a multimeter to verify continuity.
Amiga 1200 Rev 1A – Rev 2B • 1992–96
The AGA flagship. 32-bit 68EC020 CPU, 2 MB Chip RAM, AGA chipset with 256-colour modes and HAM8. Also uses SMD electrolytics that leak. Features a 2.5 " IDE header, PCMCIA slot, and 150-pin CPU accelerator slot (trapdoor). DB23 RGB video output at 15 kHz (and some VGA-compatible modes via productivity mode).
Key ICs
- CPU: Motorola 68EC020 @ 14.19 MHz (PAL)
- Alice: AGA DMA controller — replaces Agnus, 2 MB Chip RAM
- Lisa: AGA video output — replaces Denise, 24-bit palette
- Paula: 8364 — audio & I/O (unchanged from OCS)
- CIA ×2: MOS 8520
- Gayle: IDE, PCMCIA, interrupts
- Budgie: Bus buffer (Rev 1B+)
- Kickstart ROM: 512 KB (3.0 / 3.1 / 3.2)
SMD Capacitor List (Critical Recap)
The A1200 shares the same SMD electrolytic leakage problem as the A600. Recap immediately on any unrecapped board, even if it boots fine.
| Ref | Value | Voltage | Area / Notes |
|---|---|---|---|
| C401 | 100 µF | 6.3 V | Audio filter (left channel) |
| C402 | 100 µF | 6.3 V | Audio filter (right channel) |
| C403 | 22 µF | 16 V | Audio coupling (left) |
| C404 | 22 µF | 16 V | Audio coupling (right) |
| C405 | 10 µF | 16 V | Keyboard controller |
| C409 | 10 µF | 16 V | Floppy / Paula area |
| C811 | 47 µF | 16 V | 5 V filter |
| C812 | 47 µF | 16 V | 5 V filter |
| C813 | 100 µF | 10 V | Main filter |
| C821 | 47 µF | 16 V | +12 V rail |
| C822 | 47 µF | 16 V | -12 V rail |
Tip: The Rev 1A board has an additional cap (C819, 10 µF 16 V) near the IDE controller. Always cross-reference against the silkscreen on your specific board revision.
SMD Capacitor Leakage & Recapping Guide
The Amiga 600 and Amiga 1200 use surface-mount (SMD) aluminium electrolytic capacitors that are guaranteed to leak over time. The electrolyte is corrosive and will eat through copper traces, vias, and solder pads — even on boards that still appear to work. Recapping is not optional; it is a when, not an if.
1 Remove Old Caps
- Desolder all SMD electrolytics using a soldering iron with a chisel tip (or hot air at ~300 °C).
- Twist gently — do not pry, as pads lift easily on corroded boards.
- If a pad lifts, it can be repaired with fine enamelled wire soldered to the next via or trace in the circuit.
- Note the polarity marking (stripe = negative) before removing each cap.
2 Clean Corrosion
- Apply white vinegar to neutralise the acidic electrolyte residue. Let it sit for 30–60 seconds.
- Scrub with a soft toothbrush or fibreglass pen to remove corrosion from pads, vias, and traces.
- Rinse with 99% isopropyl alcohol (IPA) and allow to dry completely.
- Inspect under magnification: look for corroded vias (dark rings around holes) and broken traces.
- Use a multimeter in continuity mode to verify every trace connected to the cap pads is still intact.
3 Install New Caps
- Replace with polymer aluminium SMD or tantalum SMD capacitors (same footprint, same or higher voltage rating).
- Polymer caps do not leak, have lower ESR, and will outlast the board itself.
- Match the polarity to the silkscreen marking. Tantalum polarity is reversed from electrolytic convention (stripe = positive).
- Solder with a fine tip and flux. Inspect every joint under magnification.
A500 owners: Your board uses through-hole caps which rarely leak destructively. A recap for ESR improvement is still recommended after 30+ years, but you do not face the same corrosion emergency as A600/A1200 owners.
Video & Upscaling Reference
DB23 RGB wiring, SCART cable pinouts, 15 kHz signal specs, and modern upscaler compatibility.
DB23 to SCART Wiring RGB Cable
The Amiga outputs analog RGB at 15 kHz horizontal scan rate through a DB23 (23-pin D-sub) video port. Wire to a SCART plug for direct connection to European TVs or upscalers.
| DB23 Pin | Signal | SCART Pin | Notes |
|---|---|---|---|
| 2 | Red | 15 | 75 Ω terminated at TV |
| 3 | Green | 11 | 75 Ω terminated at TV |
| 4 | Blue | 7 | 75 Ω terminated at TV |
| 10 | CSYNC | 20 | Directly usable; or use pin 15 (HSYNC) + pin 14 (VSYNC) |
| 15 | HSYNC | — | Not needed if using CSYNC |
| 14 | VSYNC | — | Not needed if using CSYNC |
| 16 | GND (all) | 4, 5, 9, 13, 17, 18, 21 | Connect all SCART grounds |
| 17 | GND | Shell | Shield ground |
| 1 | Audio L | 6 | Left audio output |
| 13 | Audio R | 2 | Right audio output |
| — | — | 16 (Blanking) | Connect to +5 V via 180 Ω resistor to force RGB mode |
| — | — | 8 (Function Select) | Connect to +5 V via 180 Ω for 16:9 / AV switching |
Tip: Use 75 Ω series resistors on each RGB line if your Amiga revision doesn't include them on-board. The blanking signal on SCART pin 16 must be driven to ~1–3 V for the TV to accept RGB input.
15 kHz RGB Signal Specs
All standard Amiga screen modes output at approximately 15 kHz horizontal scan rate. This is not compatible with standard VGA monitors (31 kHz). You need a 15 kHz-capable display, a SCART TV, or an external upscaler/line-doubler.
| Parameter | PAL | NTSC |
|---|---|---|
| H-Sync Frequency | 15.625 kHz | 15.734 kHz |
| V-Sync Frequency | 50 Hz | 60 Hz |
| Active Lines | 256 (lo) / 512 (hi) | 200 (lo) / 400 (hi) |
| Pixel Clock | 7.09 MHz (lo) / 14.19 MHz (hi) | 7.16 MHz (lo) / 14.32 MHz (hi) |
| Colour Depth | OCS/ECS: 4096 colours (12-bit). AGA: 16.7M (24-bit HAM8). | |
| Sync Type | Composite sync (CSYNC), active-low. Directly compatible with SCART. | |
The A1200 can also output "productivity" modes at 31 kHz (Multiscan), compatible with VGA monitors, via the same DB23 port when using appropriate Workbench screen modes.
Upscaler Compatibility OSSC / RetroTINK
Modern upscalers line-double or line-triple the 15 kHz RGB signal to produce a crisp HDMI output for modern displays. Key options:
- OSSC (Open Source Scan Converter) Accepts SCART or component input. Offers 2×, 3×, 4×, 5× line multiplication. Zero latency (passthrough). Requires a display that accepts non-standard resolutions. Best paired with a custom SCART cable.
- RetroTINK 5X / 4K Accepts SCART, component, S-Video, composite. Outputs standard HDMI resolutions. Excellent scaling with minimal latency (~1 frame). Smoothing and scanline filter options. Broader TV compatibility than the OSSC.
- RetroTINK 2X-SCART Budget option. SCART in, HDMI out. Simple line-doubler, minimal configuration. Great starter upscaler.
- GBS-Control (GBS-8200 modded) Open-source firmware for cheap Chinese scalers. Surprisingly good results with custom firmware. SCART input via adapter board.
Cable quality matters. Use a properly wired RGB SCART cable with shielded signal lines and 75 Ω impedance. Cheap cables introduce noise, ghosting, and colour fringing.
Diagnostic Checklist
Power rail verification, boot screen error colour decoder, and CIA fault symptoms.
Power Rail Checks
Before powering on any Amiga, verify all voltage rails at the power connector with a multimeter.
| Rail | Spec | Tolerance | Where to Measure |
|---|---|---|---|
| +5 V | 5.0 V DC | ±5% (4.75–5.25 V) | Fuse output / near Gary or Gayle |
| +12 V | 12.0 V DC | ±10% | Serial or audio port pin |
| -12 V | -12.0 V DC | ±10% | Audio bias circuit (near Paula) |
| -5 V | -5.0 V DC | ±10% (A500 only) | Expansion port pin 14 |
Warning: If +5 V reads above 5.4 V, do NOT power on the machine. Overvoltage will damage custom chips. Check the PSU or replace it.
Boot Screen Error Colour Decoder
The Amiga Kickstart ROM performs a self-test on boot. If it fails, the screen flashes specific colours indicating the fault area.
| Colour | Meaning | Likely Cause |
|---|---|---|
| Green | Chip RAM OK | Normal — RAM test passed. If it stops here, Kickstart ROM or custom chip fault. |
| Red | Chip RAM failure | Faulty DRAM chip(s). Run memory tester via DiagROM or swap chips. |
| Yellow | 68000 CPU exception | CPU bus error, address error, or illegal instruction. Check CPU, ROM, and bus buffers. |
| Blue | Custom chip / hardware error | Agnus/Alice, Denise/Lisa, or Paula failure. Also CIA or Gary/Gayle faults. |
| White | ROM checksum failure | Kickstart ROM is corrupt or not seated properly. Reseat or replace ROM. |
| Dark grey | No valid Kickstart | ROM socket empty, ROM address lines broken, or Gary/Gayle not selecting ROM. |
| Cyan flicker | CIA or keyboard error | CIA #0 (U300) or keyboard controller not responding. Check CIA and keyboard cable. |
Tip: Flash a DiagROM to a spare ROM chip for comprehensive hardware diagnostics beyond the basic colour test.
CIA Chip Fault Symptoms (8520)
The Amiga uses two MOS/CSG 8520 CIA chips. Faults in either cause specific, identifiable symptoms.
CIA-A (U300 / Even CIA)
- Keyboard completely dead (no response to any key)
- No power LED blinking on boot
- Joystick port 1 (mouse port) not working
- Disk drive not spinning or seeking
- Parallel port dead (printer not responding)
- TOD (Time of Day) clock not incrementing
CIA-B (U301 / Odd CIA)
- Joystick port 2 not working
- Serial port dead (modem, null-modem transfers)
- Disk drive activity light always on or never on
- No audio output (CIA-B controls audio filter relay)
- Mouse moves but buttons don't register (shared with port 2)
- Overlay bit stuck — machine boots to wrong ROM address
The 8520 CIA is a DIP-40 IC, socketed on most boards. Swap with a known-good chip to confirm diagnosis. Original 8520s are becoming scarce — consider testing before assuming failure.
Connector Pinouts
Floppy, IDE/CF adapter, and expansion port pin references for the A500, A600, and A1200.
External Floppy Port DB23 Female
All Amiga models use a DB23 female connector for external floppy drives (DF1:, DF2:, DF3:).
| Pin | Signal | Pin | Signal |
|---|---|---|---|
| 1 | /RDY (active-low) | 12 | /SEL3 |
| 2 | /DKRD (read data) | 13 | GND |
| 3 | /SEL0 | 14 | /MTRX (motor on) |
| 4 | GND | 15 | /DIR (step direction) |
| 5 | /SEL1 | 16 | GND |
| 6 | GND | 17 | /SIDE (head select) |
| 7 | /SEL2 | 18 | +5 V |
| 8 | GND | 19 | /STEP |
| 9 | /CHNG (disk change) | 20 | GND |
| 10 | GND | 21 | /WPRO (write protect) |
| 11 | /TK0 (track zero) | 22 | +12 V |
| 23 | /DKWB (write data) |
Active-low signals are active when pulled to GND. Gotek floppy emulators connect to these same pins via a ribbon cable adapter.
IDE Header (2.5″ 44-Pin) A600 / A1200
The A600 and A1200 include an internal 44-pin 2.5″ IDE header for hard drives and CompactFlash adapters.
| Pin | Signal | Pin | Signal |
|---|---|---|---|
| 1 | /RESET | 2 | GND |
| 3 | DD7 | 4 | DD8 |
| 5 | DD6 | 6 | DD9 |
| 7 | DD5 | 8 | DD10 |
| 9 | DD4 | 10 | DD11 |
| 11 | DD3 | 12 | DD12 |
| 13 | DD2 | 14 | DD13 |
| 15 | DD1 | 16 | DD14 |
| 17 | DD0 | 18 | DD15 |
| 19 | GND | 20 | Key (missing) |
| 21 | DMARQ | 22 | GND |
| 23 | /DIOW | 24 | GND |
| 25 | /DIOR | 26 | GND |
| 27 | IORDY | 28 | GND |
| 29 | DMACK | 30 | GND |
| 31 | INTRQ | 32 | IOCS16 |
| 33 | DA1 | 34 | PDIAG |
| 35 | DA0 | 36 | DA2 |
| 37 | /CS0 | 38 | /CS1 |
| 39 | /DASP | 40 | GND |
| 41 | +5 V (logic) | 42 | +5 V (motor) |
| 43 | GND | 44 | GND |
CF adapter tip: Use a passive 44-pin to CF adapter. Set the CF card to "True IDE" mode if it has a jumper. Format with PFS3 or FFS via HDToolBox for best compatibility.
Expansion Ports Overview
Key expansion connectors across the three models:
A500 — 86-Pin Side Expansion
Directly on the 68000 bus. Used by memory expansions (A501), accelerators, and hard drive controllers (GVP, A590). Active-low /OVR, /INT2, /INT6 for interrupt and bus access. Pin 1 = GND, Pin 86 = +5 V.
A500 — 86-Pin Trapdoor (Bottom)
Directly maps to the expansion bus. Designed for the A501 512 KB RAM + clock expansion. Also accepts third-party memory boards and accelerators with a pass-through.
A600 — PCMCIA (68-Pin)
Type II PCMCIA slot. Used for CF card adapters, network cards, and SRAM cards. 16-bit data bus, directly managed by Gayle. Maximum 4 MB address space.
A1200 — 150-Pin Trapdoor (CPU Slot)
Directly on the 68EC020 bus. Used for accelerators (Blizzard 1230/1260, ACA-1233n) and memory expansions. Directly accesses the Fast RAM address space, bypassing Chip RAM limitations.
A1200 — PCMCIA (68-Pin)
Same as A600 PCMCIA. Type II slot managed by Gayle. Commonly used for CF adapters and CompactFlash-to-IDE bridging.
A1200 — Clock Port (Active on Rev 2B)
22-pin header originally for the RTC module. Third-party devices include USB adapters, Ethernet, and MIDI interfaces. Address range: $D80001–$D8000F.
Resources & Further Reading
Blog posts, bench tools, and community links for Amiga repair and restoration.
Smiggy's Amiga Blog Posts
Bench Tools
- IC Pinout Finder — search all retro ICs
- Recap Planner — capacitor replacement guide
- Ohm's Law Calculator
- Capacitor Code Decoder
- C64 Machine Hub — Commodore 64 reference
External Resources
- AmigaWiki — hardware & software encyclopaedia
- English Amiga Board (EAB) — largest active Amiga forum
- Aminet — Amiga software archive
- DiagROM — diagnostic ROM for Amiga hardware testing
- AmigaLove — reviews, interviews, and history