Commodore Amiga 500

This Amiga 500 Rev 6A arrived as a non-starter with a familiar history: purchased at a boot sale for £15, confirmed not working by the seller, and sent in for diagnosis. The case was in fair condition — some surface scratches and mild yellowing, particularly on the top, but no major cracks or chips.

On power-on with a known-good PSU (the original Amiga PSU was missing, which is extremely common — they tend to fail and get discarded), the machine showed a green screen instead of the expected Kickstart animation. A solid green screen on an A500 is the equivalent of a "no Kickstart" or "custom chip fault" indicator — typically Paula, Agnus, or Denise.

The internal floppy drive produced a loud grinding noise when the machine attempted to boot, suggesting a seized or broken drive mechanism. Several keys on the keyboard were physically stuck down and did not spring back.

1. Custom Chip Diagnosis
Using chip-swap testing with known-good OCS chips from my parts stock, I isolated the fault to the Paula chip (MOS 8364). Paula handles audio, disk I/O, and interrupts — its failure explains both the green screen (no valid boot signal) and the disk drive issues. The faulty Paula was desoldered and replaced with a socketed known-good unit.

2. Full Motherboard Recap
The Rev 6A board contains 10 electrolytic capacitors, several of which showed signs of leakage. All 10 were replaced with Nichicon audio-grade electrolytics. The area around each cap was cleaned of any electrolyte residue before reflowing the new components.

3. 1 MB Chip RAM Upgrade
The original A500 ships with 512 KB of chip RAM. As part of the restoration, the Fat Agnus chip (MOS 8372A) was fitted, replacing the original NTSC Agnus. Combined with a memory upgrade soldered to the motherboard, the machine now has a full 1 MB of chip RAM — the maximum addressable by the OCS chipset — improving compatibility with later Amiga software.

4. Disk Drive Rebuild
The internal drive (a Chinon FB-354 mechanism) was disassembled. The drive belt had shattered into fragments inside the mechanism — causing the grinding noise. A replacement belt (2.4mm wide, 46mm) was sourced and fitted. The drive head was cleaned with IPA- moistened foam swabs. After reassembly, the drive reads and writes 880 KB AmigaDOS disks without errors.

5. Keyboard Repair
The keyboard PCB was removed and inspected. Three key switches had broken plastic retaining clips; these keycaps were refitted with compatible replacement clips. The keyboard membrane was cleaned and all keys now return correctly. The keyboard encoder chip was reseated.

6. Case Retrobright
Top and bottom case halves, plus the function key strip, were retrobrighted over three sessions to achieve a uniform warm-cream colour. The original Amiga logo badge is intact and was carefully masked during the process to preserve its rainbow stripe colours.

After restoration, the machine boots cleanly to the Kickstart 1.3 hand-with-disk animation and then into Workbench 1.3. The DiskSalv and Amiga Test Kit diagnostics confirm all chip RAM (1 MB), fast RAM (512 KB trapdoor), and all custom chip functions are operating normally.

Audio output (via both the RCA stereo jacks and the internal speaker) is clean with no noise or hum. Several demanding Amiga 500 titles — Shadow of the Beast, Lotus Esprit Turbo Challenge, and Turrican II — were tested across multiple disks without issue.

The machine was run for 48 hours continuously before being approved for return. It's now one of the best-performing A500s I've worked on.