I didn't get as far as running the Sun Ultra 1 64-bit UltraSparc machine, but I did find the 13W3 video cable for it, and find the fault in the cable. One of the moulded-on BNC plugs (composite sync) was open-circuit. This turned out to be a bad connection under the moulded-on plastic, where the BNC plug was crimped onto the coaxail cable. That's fixable with a new BNC plug.
While looking for the MMJ cable, I found a 20GB IDE hard disk that I'd forgotten about. I've been looking for a bigger drive for the Mac G4 Sawtooth Linux machine, which currently has only 8GB. Now that I've tested it, the 20GB drive can go back into service.
By coincidence, aminorjourney went on a FreeCycle pickup to the same person who'd promised me a hulk of a laptop (Fujitsu Amilo). So, she collected the parcel with my name on it and brought it over. I now have some miscellaneous parts as well as the bit I wanted, the PS/2 trackpad. At least, I think it's PS/2; it might be USB on a modern laptop.
The real success of the day, though, was the Acorn Archimedes A310. I got it last week from a FreeCycle user in Fishponds, along with some assorted electronic junk and a PC power supply. We knew it wasn't working properly but we didn't know whether the bad video display was due to the machine or the monitor (Philips CM8833). The screen didn't sync, and the text was all in magenta. I tested the monitor on a composite video signal, and it was fine. That left something amiss in the A310's video and/or sync outputs.
After all the usual stuff with re-seating chips and checking connections, I read the manual (came with the machine) and spotted something. I'd had to replace the two AA batteries, which had burst (use-by date was 1994), and I'd cleaned up the corrosion. There's a note in the manual that tells you to switch the machine on with the DEL key held down, to re-initialise the non-volatile RAM. It also tells you to change the fan filter every year or so, but I'd just washed it out -- there was so much caked-on dust that no air flowed through it at all. Anyway, after the DEL key trick, the video display was fine and I got to a RISCOS desktop. From there, I could run games from the floppy disk. Naturally, I put the Elite disk in, but it turned out to have a bad sector. Not to be beaten at this stage, I ran the Lemmings disk instead and marvelled at what could be done with an 8MHz ARM chip and 1MB of RAM.