I’ve been working on the Archimedes

So for the last week I’ve mostly been concentrating on something else but I have spent some time on the new Archimedes. It’s an Archimedes 440, one of the original family, but it has some upgrades installed. Most noticable is the CPU has been upgraded to an ARM 3 processor, and the OS ROMs had been upgraded to RISC-OS 3 as well.

First steps first, I needed to inspect what I had, and let me tell you, this system has seen some horrors.
Firstly, one of the daughterboards (Lovingly called “Podules”) had a Varta battery on it, which had reached “End of Life” and had dumped it’s gust all over the Podule. It’s a writeoff, but thankfully neither hugely important, nor significant. It also doesn’t appear to have got onto the motherboard, so that’s a plus.
Secondly, the batteries for the main board (which were off to one side) were standard alkalines and had, at one point, rotted and split. The case has sustained extensive damage, but thankfully, so far, it’s been surface damage I’ve been able to treat with vinegar, followed by distilled water, followed by isopropyl alcohol.

There’s also some damage to the main board and this is where I have been concentrating my efforts, so far. There were some tracks on the top that looked “dodgy”, eg attacked by acid. I have cleaned off any discoloured tracks back to copper, cleaned, checked for continuity and covered with “lacquer” (Eg nail polish) to stop further oxidation.

There is also extensive discolouring of the solder on the underside of the RAM are of the board. I tried to reflow it a bit but it’s quite stubborn.

At this point I decided I needed to “bite the bullet” and plug it in and turn it on. I had already stripped it down to clean and desolder, plus I had tested voltages coming out of the PSU.
I was greeted with a red screen. According to the super helpful people over on StarDot, this is actually a good sign! It means the CPU is booting. Next step was to plug the floppy drive in and see what happens. Oddly I got nothing. Further investigation showed a PSU with a low 12v line. This usually means a short somewhere. StarDot to the rescue and I carefully snipped out one of the capacitors (C37) which is apparently well known for going open circuit. The system can run without one smoothing capacitor for quite some time. Long term it’ll need a replacement.

So now I had a system that would start to boot then stop. The Archimedes has a very clever system of self diagnostics where it flashes the floppy light in a series of short and long flashes in sets of four. You can then feed these into a special web page that decodes the error.

As I wasn’t getting a full set of codes, I needed to do more work on the system. I cleaned contacts on the bottom of the RAM and cleaned up connectors on the CPU board and finally got it booting long enough to display a series of flashes.
They were:

∙∙∙∙
∙∙∙∙
∙∙∙∙
∙∙-∙
∙∙∙∙
∙∙∙-
∙∙∙∙
∙∙∙-

Which, plugging into the POST error calculator gave me:
RAM control line failure
CMOS RAM checksum error
Self-test due to power-on
So we’re getting somewhere!

At this point I attempted to build a keyboard adapter that’ll allow me to plug in a PS/2 keyboard and mouse so I can at least get the past the CMOS error. It wasn’t too hard, and was based on a commonly available PIC processor so I had that built in a day.

I reassembled everything and tried it again and…

Nothing. Not even the red screen.

At this point I’m stumped. Something else has failed and it’s not even getting to POST. I’ll tackle the corrosion some more on the bottom of the RAM and see if I can get further but maybe I have killed it somehow?

The hardest thing is I don’t have anyone else in the state that can assist. These are rare systems and without a second system, I don’t even know if my keyboard adapter is working or not…

All in all, a bit of a frustrating outcome, but all part of the hobby I guess.

Published by ilike8bits

I collect old computers and consoles

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