Acorn Risc PC 700 Refurb

My friend Steve, who I worked with, gave me one of his two Risc PC's… it was a good one, too:

  • Risc PC 700
  • 64MB RAM
  • 2MB VRAM
  • Ethernet module
  • StrongARM 200 processor card
  • AlephOne DX2-80 second processor card
  • IDE hard drive

I hadn't done anything with it, until getting the computer shelving in place, then tried turning it on for the first time.

Sadly it didn't work - although the OSSC and KVM detected a signal from it, I got nothing but a blank, 50Hz video feed and the noise of the original IDE disk spinning up. So I decided to open it up and take a look….

Oh dear. That will be one completely failed battery cell. With nasty battery gunk coming out.

First job is to remove the power supply, to get access to remove the battery and get a closer look at the board… it's held in with one screw, into a screw post in the case…

… which disintegrated as soon as I looked at it!

Fortunately the battery was easy to snip off…

… at first glance the board appears relatively unscathed. A quick clean up with some thinners to get the bulk of the nastiness off, and then a little bit of vinegar to neutralise any remaining corrosion from the battery leak

Next task is to try powering it on again with just the basic peripherals connected.

The mainboard itself looks okay, no signs of any other corrosion or similar.

Unfortunately it looks like this one hasn't aged too well either; on removal of the card from the processor slot, one of the surface mount capacitors literally dropped off the card. It looks like it has been hanging on purely by the residue of the cap itself. Urgh.

This one is going to need a clean up and a replacement surface mount cap fitting. Oh what fun! :(

The StrongARM card looks fine:

The ethernet module is by ANT, and comes with a ROM labelled as 'Access / AUN / TCPIP'… which of these it has enabled (back when Acorn networking modules were sold, you had to pay for the additional features).

I won't know what is enabled on it until I can get the system up and running again. Again, no visible damage from the battery leak.

Two sticks of what appear to be a 8MB and 32MB SIMM were fitted to the machine.

The first one is an unusual one in that it has sockets for additional DRAM chips to be fitted - I guess it meant the manufacturer only had to produce one board design:

The second module is a more traditional design:

The Risc PC was the first design from Acorn to have dedicated video memory; all other models sharing video RAM with main memory. You could have 0MB, 1MB or 2MB module installed. This Risc PC 700 has the extra fancy 2MB module which allows higher resolutions and colour depths:

Again, no visible damage from the battery leak.

This is the riser that allows add-in cards to be fitted.

No damage seen.

Not sure of the original purpose of this card, but it was fitted and appears to have no damage from the battery leak:

I reassembled a minimal system:

  • Power supply
  • Main board
  • StrongARM processor
  • 8MB SIMM

Pressed the power button holding 'Del' (CMOS reset routine for the Acorn) and crossed my fingers:


At this point it wouldn't boot to the desktop, so I tried hooking up the disc drive and gave it a reset:

Even better! There seems to a working OS install on the drive as I saw various messages about plugins and toolboxes being loaded from the drive. Sadly it didn't give me a fully working desktop as it eventually threw this error in my face:

To be honest I'm not surprised an old 800MB IDE drive from-gods-know-when has a few errors. The plan would be to swap it out (or, preferably, leave it installed but unplugged) with a compact flash card reader instead.

Just a bit of soap and water and a magic eraser block:

It's been a long time since I've done it, so this is also for my own peace of mind.

Steps to reinstall Risc OS to hard drive

  • Unzip the !SparkPlug zip file, and copy the self-extracting .bas file to a DOS floppy
  • Run SparkPlug from RAM
  • Copy ! to a DOS floppy
  • Unpack !HForm to RAM
  • Format your new drive, make it bootable
  • Copy !SparkPlug to the formatted hard drive
  • Copy ! to a DOS floppy
  • Unpack ! and copy to your formatted hard drive
  • Use the MS-DOS SPLIT.EXE on the PC side (included in addition to versions for other platforms) to split the Risc OS 3.7 universal boot sequence into two 1.4MB images (pre-split version)
  • Copy each image on a single DOS floppy to the Risc PC
  • Re-join the two split files using !Split and drag the unzipped !Boot sequence to your hard drive

All working, but for some reason at 1024×768 either my OSSC or monitor cuts off a good chunk of the left hand side of the screen:

… one more thing to look at!

To do!

  • blog/bbc_riscpc_fix.txt
  • Last modified: 2020/07/28 19:05
  • by john