The cage isn't a problem on these. The backplane is symmetrical so to work on them you just remove all the boards, unscrew the backplane from the cage and then just make up a bunch of wooden separators to ensure you don't short anything out. Bung the board you need to work on the top and voila!
I fixed a few G80 sets for Ordy before we moved house as it goes (jeebus, that makes it 6+ years ago!!!) pain in the arse hardware wise because I'd get a set working and then by the time I'd fixed one fault another would appear and so on, but got there in the end. I think there's a load of interrupts between the boards as well...
All good fun, you'd lap it up
[EDIT] I've got a bunch of notes somewhere. And the Astro Blaster set I kept as payment is still up in the loft propping our TV arial up at the right angle
guddler2013-11-10 13:17:01