Troubleshooting Superbrains

Hello folks, I picked up a couple of Intertec Superbrains last week, and have finally got around to cracking the cases. One has memory problems, the other has keyboard problems. I'm fairly sure the one with memory problems is down to a faulty 4116, but I can't work out how to find out which one it is. I'm guessing it's in the lower part of memory, because although the system boots it hasn't got enough marbles to run DDT.COM - if I could get that working I could prod around in memory until I found the stuck bit. The keyboard problem on the other one is a bit odd - not all the keys work (haven't worked out the pattern but it *seems* like the outer three on the ends of each row work, the middle ones being dead), and the key repeat starts instantly. I'm a tad concerned that this is a sign of a dying keyboard controller chip - I doubt I'll ever find another, although if it was a problem I'd just program up a PIC to do its job. Any thoughts? Is there a way to trick CP/M into loading DDT into higher memory? Gordon