1992 Acorn Archimedes 3010 Repair & Restoration

Earlier in 2024, I bought a large lot of very interesting vintage electronics – including test gear, computers, and audio equipment – which belonged to a local electronics engineer, who had sadly passed away quite recently, and whose family wanted it to go to a good home.

Among this was a very nice Acorn Archimedes 3010 in good condition and came with several accessories including its original box, as well as a matching Acorn AKF-17 CRT display also with its original box, however both of these were bought sold-as-seen.

The A3010 was released in 1992, as one of several new models (A3010/A3020/A4000) introduced to complement the A3000 and to replace the low-end A400 series. These utilised the first ARM SoC – the ARM250 – a single-chip design including the functionality of an ARM2 (or ARM3 without cache), the IOC1, VIDC1a and MEMC1a chips integrated together. The ARM250, running at a higher 12 MHz clock frequency and used with faster 80ns RAM, compared to the 8 MHz of the ARM2 and 125ns RAM of the A3000, gave a potential 50% performance increase, achieving a reported 7 MIPS.

The A3010 had good sales in the UK and was used in a lot of educational establishments as a part of the BBC’s Computer Literacy Project, so they are not too difficult to find – there are usually a few up on eBay at any one time, but they often command high sale prices.

Unfortunately, the A3010 (and other machines of the era with a battery-backed RTC, such as the Amiga 500+ and Acorn A3000) have Varta rechargeable NiCd batteries soldered to the mainboard which leak a corrosive alkali (potassium hydroxide), even during storage.

This corrosive material is notorious for killing machines because it eats away at the PCB, causing damage to ICs, sockets, traces, vias, connectors, and components. These types of batteries should therefore be removed and disposed of as soon as possible.

As such, I didn’t even attempt to power up the computer in its current condition. Instead, I opened the computer for inspection, which is a relatively simple procedure as the case is only held together with three clips and three screws.

The keyboard can then be removed – this is held in place by plastic alignment posts and its two ribbon cables, which are quite fragile so must be removed carefully.

The rest of the electronics (mainboard, PSU, and 3.5″ FDD) comprise a single assembly held together by an upper and lower RF shield. This assembly is held into the case by three screws on its front edge – two ae Philips, the middle is torx.

With the assembly removed, there was evidence of corrosion on the RF shield near the RTC battery in the top-right corner, underneath the FDD.

The upper RF shield holds the speaker and FDD, and latches into place against the lower RF shield – to separate the two halves of the shield, unplug the FDD ribbon and power cables, and the upper of the shield part should just slide off forwards; the speaker cable can then be unplugged.

After getting access to the mainboard, it seemed that the battery leakage was (luckily) limited to the very top-right corner of the board and the inside of the lower RF shield.

This being the case, I was hopeful that the repair would just require cleaning up the battery leakage and fitting a new RTC battery.

Past this point I’d recommend wearing a set of nitrile gloves, and cleaning your hands, tools, and workspace regularly, as battery alkali is pretty nasty stuff.

The first step was to remove the source of the corrosive material: the battery itself. I used a small pair of clippers to cut its three legs close to the battery casing (leaving enough length on its legs to help with desoldering), taking care not to cause damage to the board – then, I pulled it off and put it straight in the bin.

I removed the board for improved access, which also allowed me to inspect the underside for further damage – the board is held into the RF shield by the eight hex screws on the rear ports, once removed the board should lift out.

The second step was to neutralise the remaining corrosive material. I bathed the affected area in white vinegar for a while to neutralise the battery alkali, scrubbing it gently with an toothbrush – then, I washed the board off with 99.9% IPA to remove the leftover alkali salts and vinegar, then left the board to dry off.

The third step was to do an initial inspection and clean-up of the battery damage. Thankfully, the corrosion was rather minor – the battery traces and vias were intact and I just needed to scrape off some damaged solder mask and a bit of corrosion on the parallel port. I also removed the battery legs using my desoldering station (a Duratool D00672) and a large amount of leaded solder and rosin flux, necessary because the corroded material on the affected solder joints makes them difficult to work on.

I then installed a CR2032 battery and holder, which is a direct replacement for the original battery and features a built-in diode to prevent back-charging. I opted for this over a soldered rechargeable NiMH battery because coin cells are very easy to remove or replace – the original battery was a 1.2V 280mAh NiCd cell, but the PCF8583P CMOS RAM chip used by the A3010 accepts a wide supply voltage range (1V to 6V), so a large number of suitable replacement batteries are available.

I reinstalled the mainboard for initial testing, now that the RTC battery had been repaired – this was just the reverse of its disassembly.

I connected the machine up to a suitable display and powered it on, whilst holding the delete key to reset the contents of the PRAM, and it booted correctly into the desktop.

However, I found that the machine would boot intermittently when powered on or reset – about half the time it would drop into the supervisor giving data transfer errors.

Due to the nature of the error messages, it seemed likely that this was a RAM issue – the machine had a Simtech 3MB RAM expansion fitted taking it to the maximum of 4MB RAM, which could be causing the intermittent boot problems.

I removed the 3MB RAM expansion, and it had one pin bent at 90 degrees as though it had been crushed outwards during installation – I’m certain that I couldn’t have done this while removing the expansion, so it’s quite likely that it had been this way since the expansion was first installed, probably in the 1990s. If that is in fact the case, this machine must have been pretty unreliable even back in the day, as this pin will have been making intermittent contact for near enough the entire lifetime of the computer!

I tried carefully bending the pin back into place, but due to these types of pin being so delicate and the sheer bend radius, it unfortunately snapped off – not surprising.

To test my assumption about the RAM expansion causing the boot problems, I set the RAM jumpers for the default 1MB and tested the machine without the RAM expansion installed – sure enough, it booted reliably every time.

I managed to repair the expansion by desoldering the remnants of the original pin, flipping it around, and soldering it back into place using its via as an SMD pad. This was quite tricky to do as the pins are held in place with kapton tape and access for an iron is limited.

With the repaired RAM expansion installed and the jumpers set correctly for 4MB RAM, the computer now booted reliably with 4MB RAM registered under RISC OS.

After all this work was performed, I did some finishing up: I thoroughly cleaned the mainboard with compressed air and an ESD-safe brush; I thoroughly cleaned the case inside and out using Cillit Bang general-purpose degreaser, a microfibre cloth for large areas, and a toothbrush for small areas; I cleaned the read/write heads on the internal 3.5″ FDD using a head cleaning disk, in case the drive was dusty or dirty; I also disassembled and cleaned the keyboard.

The computer still seemed to boot OK following all of my modifications. However, just because a computer boots, that doesn’t mean it’s working properly. Thorough testing is necessary to verify correct operation, so I did as much testing as I could.

• All keys register correctly.
• Internal 3.5″ FDD reads and writes from/to disks OK.
• RGB video output works OK.
• Composite video output works OK.
• Stereo audio output via internals speakers works OK.
• Dedicated headphone output works OK.
• All mouse inputs (four directions, three buttons) work OK.
• Internal 1MB RAM expansion works OK.
• Onboard battery-backed RTC works OK.
• Status LEDs (power, drive activity) work OK.
• Serial interface works OK.
• Reset button works OK.

Another restoration complete, and an Acorn Archimedes 3010 saved!