Amiga 1200 Restoration & Upgrades

I’ve been slowly but surely branching out into Amigas from Commodore’s 8-bit range of computers, and as such I recently got my hands on my first Commodore Amiga 1200.

The A1200 is a 32-bit computer from the 1990s, and is effectively a more capable version of the A600, featuring a 14MHz 68020 CPU (as opposed to an 8MHz 68000), 2MB Chip RAM (as opposed to 1MB) and AGA graphics (as opposed to ECS graphics), and a full-sized keyboard – like the A600, it also features an onboard IDE and PCMCIA interface.

This A1200 was a bit of a basket case, not only in need of a good clean and service, but also some repairs – the computer booted correctly but had distorted audio, and the internal 3.5″ FDD would not load disks (even in another machine).

As it turned out, both of these faults were down to the Achilles’ heel of the later Amigas. Unlike the A500 which was manufactured using through-hole electrolytic capacitors, the A1200 and its little brother the A600 primarily use surface-mount (SMD) electrolytic capacitors – these capacitors are especially unreliable and frequently leak, causing a lot of problems in this era of computers.

I therefore replaced all of the electrolytic capacitors on the mainboard using new capacitors with a solid electrolyte, which won’t suffer from leakage in future – see my general advice for capacitor replacement for more detailed information on the process.

The mainboard needs to be removed from the case, and the RF shield and plastic insulating layer removed by undoing the fixing nuts on the rear ports. I typically desolder the keyboard connector as this gives better access to the two SMD capacitors along the rear edge of the mainboard.

After testing, the A1200 appeared to be working fine again – happy days! Time for some upgrades – both for cosmetics and for performance.

First off, I dismantled and thoroughly cleaned the case and keyboard.

I also dismantled, cleaned, and lubricated the original FDD (a TEAC FD-235F), but this didn’t solve the disk loading problem. The FDD appeared to be mechanically fine, so the problem was likely electrical: I cleaned all the connectors to no effect; I then noticed that an SMD electrolytic capacitor on the drive logic board was quite crusty, so decided to replace all the electrolytic capacitors in the drive (a 4.7uF 25V SMD and a 100uF 10V radial). After doing so, the drive started working perfectly.

Then, I fitted a KickStart 3.1 ROM, internal IDE-CF adaptor, and an internal WorkBench 3.1 CF card, allowing internal storage without the need for a HDD; I also fitted an 8MB Fast RAM expansion with onboard RTC and 40MHz FPU.

Soon I’ll be treating the keyboard for yellowing, and fixing the PCMCIA reset issue.

I’ve also had an Amiga 600 on the bench – pictured below alongside the A1200 – also requiring a recap. This has already featured on the blog, here.