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.

AreaTypical ValuesNotes
Main filter1000 µF 16 V, 470 µF 16 V5 V rail bulk filtering
Audio path10 µF 16 V ×4Coupling caps near Paula; affects audio quality
Video47 µF 16 V, 10 µF 16 VRGB output filter & composite encoder
Floppy10 µF 16 VDrive controller decoupling
Keyboard22 µF 16 V, 47 µF 16 VKeyboard controller filter

Replace with 105 °C low-ESR electrolytics. No SMD cleanup needed on standard A500 boards.

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

  1. Desolder all SMD electrolytics using a soldering iron with a chisel tip (or hot air at ~300 °C).
  2. Twist gently — do not pry, as pads lift easily on corroded boards.
  3. If a pad lifts, it can be repaired with fine enamelled wire soldered to the next via or trace in the circuit.
  4. Note the polarity marking (stripe = negative) before removing each cap.

2 Clean Corrosion

  1. Apply white vinegar to neutralise the acidic electrolyte residue. Let it sit for 30–60 seconds.
  2. Scrub with a soft toothbrush or fibreglass pen to remove corrosion from pads, vias, and traces.
  3. Rinse with 99% isopropyl alcohol (IPA) and allow to dry completely.
  4. Inspect under magnification: look for corroded vias (dark rings around holes) and broken traces.
  5. Use a multimeter in continuity mode to verify every trace connected to the cap pads is still intact.

3 Install New Caps

  1. Replace with polymer aluminium SMD or tantalum SMD capacitors (same footprint, same or higher voltage rating).
  2. Polymer caps do not leak, have lower ESR, and will outlast the board itself.
  3. Match the polarity to the silkscreen marking. Tantalum polarity is reversed from electrolytic convention (stripe = positive).
  4. 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 RGB Video to SCART Wiring RGB Cable

The Amiga outputs analog RGB at 15 kHz horizontal scan rate through a DB23 (23-pin D-sub) RGB video port. Wire to a SCART plug for direct connection to European TVs or upscalers.

DB23 PinSignalSCART PinNotes
2Red1575 Ω terminated at TV
3Green1175 Ω terminated at TV
4Blue775 Ω terminated at TV
10CSYNC20Directly usable; or use pin 15 (HSYNC) + pin 14 (VSYNC)
15HSYNC—Not needed if using CSYNC
14VSYNC—Not needed if using CSYNC
16GND (all)4, 5, 9, 13, 17, 18, 21Connect all SCART grounds
17GNDShellShield ground
1Audio L6Left audio output
13Audio R2Right 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.

ParameterPALNTSC
H-Sync Frequency15.625 kHz15.734 kHz
V-Sync Frequency50 Hz60 Hz
Active Lines256 (lo) / 512 (hi)200 (lo) / 400 (hi)
Pixel Clock7.09 MHz (lo) / 14.19 MHz (hi)7.16 MHz (lo) / 14.32 MHz (hi)
Colour DepthOCS/ECS: 4096 colours (12-bit). AGA: 16.7M (24-bit HAM8).
Sync TypeComposite 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, and inspect for SMD capacitor ripple or clock corrosion on the oscilloscope:

RailSpecToleranceWhere to Measure
+5 V5.0 V DC±5% (4.75–5.25 V)Fuse output / near Gary or Gayle
+12 V12.0 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.

ColourMeaningLikely Cause
GreenChip RAM OKNormal — RAM test passed. If it stops here, Kickstart ROM or custom chip fault.
RedChip RAM failureFaulty DRAM chip(s). Run memory tester via DiagROM or swap chips.
Yellow68000 CPU exceptionCPU bus error, address error, or illegal instruction. Check CPU, ROM, and bus buffers.
BlueCustom chip / hardware errorAgnus/Alice, Denise/Lisa, or Paula failure. Also CIA or Gary/Gayle faults.
WhiteROM checksum failureKickstart ROM is corrupt or not seated properly. Reseat or replace ROM.
Dark greyNo valid KickstartROM socket empty, ROM address lines broken, or Gary/Gayle not selecting ROM.
Cyan flickerCIA or keyboard errorCIA #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:). See also DB23 RGB Video, 5-Pin Square DIN Power, 44-Pin 2.5″ IDE & 34-Pin Gotek, DB9 Mouse/Joystick, and DB25 Serial.

PinSignalPinSignal
1/RDY (active-low)12/SEL3
2/DKRD (read data)13GND
3/SEL014/MTRX (motor on)
4GND15/DIR (step direction)
5/SEL116GND
6GND17/SIDE (head select)
7/SEL218+5 V
8GND19/STEP
9/CHNG (disk change)20GND
10GND21/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.

PinSignalPinSignal
1/RESET2GND
3DD74DD8
5DD66DD9
7DD58DD10
9DD410DD11
11DD312DD12
13DD214DD13
15DD116DD14
17DD018DD15
19GND20Key (missing)
21DMARQ22GND
23/DIOW24GND
25/DIOR26GND
27IORDY28GND
29DMACK30GND
31INTRQ32IOCS16
33DA134PDIAG
35DA036DA2
37/CS038/CS1
39/DASP40GND
41+5 V (logic)42+5 V (motor)
43GND44GND

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

External Resources

Commodore Amiga 1987 · 16/32-Bit Computers

Amiga 500 / 600 / 1200 — Unified Workbench Reference

A500 Rev 3–8A, A600 & A1200 SMD capacitor leakage guide, boot screen colour decoder, DB23 RGB SCART wiring, and custom chip pinouts.

CPU / Architecture MC68000 / 68EC020 @ 7–14 MHz
Memory (RAM / VRAM) 512 KB – 2 MB Chip RAM
Capacitor Mount Through-Hole (A500) / SMD (A600/A1200)
Custom Chipset & Key ICs
MC68000 Fat Agnus 8372/8375 Denise / Lisa Paula 8364 8520 CIA Gary / Gayle
Capacitor & Power Stage Reference

Amiga A500 / A600 / A1200 — Capacitor & Recap Reference

Board revisions, electrolytic capacitor lists, voltage/farad ratings, and Through-Hole (A500) / SMD (A600/A1200) servicing notes.

Amiga A500 / A600 / A1200 — Printable Board Recap & Capacitor BOM ReferenceFormat this system's capacitor replacement list, diagnostic flowchart, and IC pinouts into a high-contrast bench PDF.

Amiga 500 — Rev 6A / Rev 7

Late A500 mainboard • Mount: Through-hole • Difficulty: Beginner friendly

Full Printable Recap Sheet →

Mainboard (17 Capacitors)

Ref Capacitance Voltage Package / Type Circuit Location & Bench Notes
C303 22 uF 50 V Radial
C304 22 uF 50 V Radial
C306 10 uF 50 V Radial
C307 470 uF 25 V Radial 470 uF on this revision. The Rev 3 / Rev 5 boards use 100 uF at C307.
C324 22 uF 50 V Radial
C334 22 uF 50 V Radial
C401 3300 uF 25 V Radial One of the two largest cans on the board. Watch the height under the keyboard.
C402 3300 uF 25 V Radial One of the two largest cans on the board.
C712 10 uF 50 V Radial
C811 100 uF 50 V Radial
C812 100 uF 50 V Radial
C813 100 uF 50 V Radial
C814 100 uF 50 V Radial
C815 100 uF 50 V Radial
C816 100 uF 50 V Radial Present on Rev 6A / 7 only - the earlier boards stop at C815.
C821 47 uF 50 V Radial
C822 47 uF 50 V Radial
Printable Diagnostic Flowchart & Voltage CheckpointsFormat this step-by-step fault isolation tree into a high-contrast bench reference sheet.

Complete Diagnostic Flowchart: Amiga 500/600/1200 Boot Color Code, Chip RAM & Audio/Video Isolation (Commodore Amiga 500 (Rev 3/5/6A) / A600 / A1200)

STEP 1: Check Amiga PSU Rails (+5V, +12V, -12V) & 68000 Pin 18 (/RESET) [node-1]
Measure +5V DC at MC68000 (U1) Pin 14 (VCC) and Pin 18 (/RESET) + Pin 17 (/HALT). Verify /RESET and /HALT rise cleanly from 0V to +4.8V ~500 ms after power-on.
Expected Reading: +4.85V to +5.15V DC on VCC; Pin 18 (/RESET) and Pin 17 (/HALT) steady HIGH (+4.8V).
STEP 2: Does the Screen Stop on GREEN (Chip RAM / Agnus) or Boot with Distorted Audio? [node-2]
Observe the RGB / Composite screen during boot: Dark Grey -> Light Grey -> White -> Kickstart screen. Choose YES if the screen turns GREEN (Chip RAM error) or stays Black/Dark Grey; choose NO if the system boots to Workbench/Kickstart with quiet/distorted audio or flickering video.
Expected Reading: YES = Isolate Fat Agnus (U2 PLCC-84) & Chip RAM / A501 Varta corrosion; NO = Isolate Paula audio coupling caps (C324/C334).
[ISOLATED FAULT: RES-AMIGA-RESET] Fault Isolated: 68000 Double Bus Fault (/HALT Low) or Kickstart ROM / CIA1 U7 VERDICT
The 68000 CPU is halting immediately after reset because it cannot read valid vectors from Kickstart ROM (U6) or CIA1 (U7 8520) /OVL overlay pin.
[ISOLATED FAULT: RES-AMIGA-GREEN-RAM] Fault Isolated: Green Screen — Chip RAM (U16–U19) or Fat Agnus (U2) Socket Contact VERDICT
Kickstart's early self-test detected a failure in the lower 256KB/512KB Chip RAM or DMA address multiplexing through Fat Agnus (U2).
[ISOLATED FAULT: RES-AMIGA-AUDIO-CAPS] Fault Isolated: Leaking Audio Coupling Capacitors (C324/C334) & LF347 Op-Amp Bias VERDICT
Tinny, quiet, or distorted left/right audio channels with a working boot screen are classic symptoms of dried-out 22µF bipolar/electrolytic audio coupling caps and -12V op-amp supply issues.
Interactive Pinouts, Visualizers & Disassemblers

Amiga A500 / A600 / A1200 — System Bench Tools & IC Pinouts

Click any chip below to open its interactive DIP/PLCC pinout diagram, pin-by-pin signal table, and oscilloscope test waveforms.

Amiga A500 / A600 / A1200 — Printable IC Pinout & Chipset SummaryPrint this system's custom IC pinout summary or open any chip card below for its full DIP/PLCC pinout sheet.
DIP-14 74-Series Gates

74LS14

SN74LS14N / DM74LS14N

Hex Schmitt-trigger inverter — six NOT gates with hysteresis, the standard cure for slow or noisy input edges.

Open Interactive Pinout →
DIP-20 74-Series Bus Interface

74LS244

SN74LS244N / DM74LS244

Octal 3-state buffer/line driver — two 4-bit groups with separate active-low enables, interleaved down the package.

Open Interactive Pinout →
DIP-20 74-Series Bus Interface

74LS245

SN74LS245N / DM74LS245

Octal bidirectional 3-state bus transceiver — one direction pin and one active-low enable, the standard bidirectional bus driver.

Open Interactive Pinout →
DIP-20 74-Series Bus Interface

74LS373

SN74LS373N / DM74LS373

Octal transparent latch with 3-state outputs — level-sensitive latch enable on pin 11, the standard address latch for multiplexed buses.

Open Interactive Pinout →
DIP-20 74-Series Flip-Flops

74LS374

SN74LS374N / DM74LS374

Octal edge-triggered D flip-flop with 3-state outputs — rising-edge clock on pin 11, the standard registered bus driver.

Open Interactive Pinout →
DIP-14 4000-Series Gates

CD4093

CD4093B / MC14093 / HEF4093

Quad 2-input NAND gate with Schmitt-trigger inputs — CMOS, follows the CD4011 pinout, the cure for slow or noisy input edges.

Open Interactive Pinout →
DIP-64 Motorola 68000

Motorola 68000

MC68000 / MC68HC000

16/32-bit CPU at the heart of the Amiga, Atari ST, original Macintosh and Sega Mega Drive.

Open Interactive Pinout →
DIP-40 MOS 6500 Peripheral

MOS 6526 CIA

MOS 6526 / 6526A / 8521

Two 8-bit I/O ports, two timers, a time-of-day clock and a serial port — the C64 peripheral chip.

Open Interactive Pinout →
PLCC-84 Commodore Amiga Custom

MOS 8372A / 8375 Fat Agnus

MOS 8370 / 8371 / 8372A / 8375 (PLCC-84)

The central DMA, Blitter, Copper and Chip RAM controller of the Amiga 500, 2000 and 3000 — 25 DMA channels, RGA register bus, and 512KB/1MB/2MB Chip RAM addressing.

Open Interactive Pinout →
DIP-48 Commodore Amiga Custom

MOS 8362 Denise / 8373 Super Denise

MOS 8362R8 (OCS) / 8373R4 (ECS Super Denise)

The Amiga's Display Encoder — renders 6-bitplane HAM/EHB playfields, 8 hardware sprites, 12-bit (4096-colour) RGB output, and quadrature mouse counters.

Open Interactive Pinout →
DIP-48 Commodore Amiga Custom

MOS 8364 Paula

MOS 8364R4 / 8364R7 (DIP-48 & PLCC-52)

The unchanged sonic heart of every Amiga from the 1985 A1000 to the 1992 A4000 — 4-channel 8-bit DMA audio, MFM floppy controller, interrupt controller, UART, and proportional pots.

Open Interactive Pinout →
DIP-28 EPROM

27128 / 27256 EPROM & CPC 40009 System ROM

Amstrad 40009 / 27C128 (16KB) / 27C256 (32KB) / 27C512

16KB (27128) and 32KB (27256) JEDEC 28-pin ROM/EPROM — direct drop-in replacement for the Amstrad CPC 464's 32KB OS + Locomotive BASIC ROM (IC103, part 40009).

Open Interactive Pinout →
DIP-8 Operational Amplifier

LM358 dual op-amp

LM358 / LM358N / LM2904 / LM158 / LM258

Dual op-amp, single-supply. The two halves are MIRRORED — inputs swap round between them. Output cannot swing all the way to V+.

Open Interactive Pinout →
DIP-16 Line Driver

Maxim / TI MAX232

MAX232 / MAX232A / MAX232I / SP232 / ICL232

Dual RS-232 driver/receiver — generates +/-10 V from a single +5 V rail. Six of sixteen pins carry no signal (charge pump and caps).

Open Interactive Pinout →
DIP-8 555 Timer

NE555

NE555 / LM555 / SA555

The classic 555 timer — astable, monostable and bistable modes from a single 8-pin chip.

Open Interactive Pinout →
Visualizer

Signal & Trace Visualizer (Scope)

Compare healthy vs. faulty CPU clocks, reset ramps, PLA strobes, and 5V PSU ripple waveforms.

 Disassembler & ROM Lab

Retro File Utilities (Rust/Wasm)

6502/6510 disassembler with IC register links, C64 .D64 parser, and EPROM CRC32 verifier/patcher.

 Logic & Pinouts

Connector & Port Pinout Reference

59 interactive RGB SCART, DIN A/V, PSU polarity, joystick, floppy, and expansion bus pinouts.

 Logic & Pinouts

Logic & RAM Substitution Guide

Cross-reference 4116→4164 DRAM mods, 2364→27C256 EPROM adapters, and 74LS/74HCT swaps.

Theme Palette

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Clean light mode

Audio & Display

Relay Click Sounds Web Audio API — soft mechanical clicks
CRT Scanline & Flicker Pure CSS overlay effect

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