I've just dug out a C128DCR I ended up with a while ago - one of those 'tested and it does X,Y and Z' deals where X,Y and Z seem to be about the only things it does when you get hold of it.
The current state of play is:
*Boots into C64 mode with the commodore key held down, 38911 bytes free, seems to work okay other than the disk drive light is permanently on and the drive motor seems to be permanently on (albeit slowly). Any drive commands, such as 'load"$",8' lock it up
*Boots into 128 mode (40 column) with the right amount of free memory shown, but won't respond beyond that - I'm assuming it's waiting on the diskdrive at this point.
*I'm assuming the 128 should just start from a cartridge the same way a C64 did? If I start the machine with a cartridge plugged it I either get a C64 screen with 38911 bytes free, or with a reduced amount (I'm assuming that's down to the state of the memory configuration lines?).
Any ideas where I should start troubleshooting this? I seem to remember in the 1541 that kind of drive behaviour was down to a dead 6522 but I'm not sure if the 128D is the same in that respect.