Was working on the RT + new Linux box and got bored during an install. Disconnected the 50Z PSU, and it powered up, went looking for shorts and found a tantalum cap with 0.2 ohms across it's centre and outer pins. Removed it, 50Z is running fine again
Had two visual black dots and with three legs - looked like an orange ghost from PacMan.
p.s. as much as I despised the PS2 series when younger, the whole "clip clip" thing with the PS/2 50 is awesome - takes like 30 seconds to dismantle it right to the motherboard.