Tony, I have the PCjr Technical reference too and it covers the pinouts of the expansion bus, but not the 3rd party expansion unit itself. I have no documentation for that beast. It sounds like I should buy some soldering/desoldering equipment and start practicing. The broken pin is in the bottom row of the connector, so I don't have easy access to remove it in place. Were you suggesting that I only cut away part of the connector, leave the rest intact, and then replace the part that I cut away? That would certainly save a lot of work, since it is 30 pins across and this pin is second from the outside. Now the power supply is a trickier problem. The PCjr power supply has an external transformer, then another stage inside. The expansion unit looks to have the same setup, except I don't have the external transformer. Since it has the same connector as the standard PCjr power supply, I grabbed a spare PCjr power supply and used it. It's possible that the input voltage is wrong, thus causing the second stage inside the expansion unit to do the wrong thing. So here's the $64000 question - does a Rapport Drive II expansion chassis use the same power supply as the PCjr? If not, can anybody tell me what the true power supply behaves like? Back to assuming I've got the correct external transformer ... I checked all of the boards on the expansion chassis, and I didn't see any burn marks. Does that mean I have no shorts on the board ? ;-) I know what a short is, especially when it starts vaporizing wire, but how do I diagnose a short on something that looks pretty clean and isn't doing anything obvious? I need to find if that pick line is going active - that might be the key to my problems. I'm really thinking of putting an external supply on it, just to test to make sure that it really is the power supply that is acting up. If the rest of it works, then I can relax and take my sweet time with the power supply. (I'm a glutton for punishment. I've got 6 danged PCjrs in the house, all in some state of disrepair. I'd like a good working one. Next time I'm going to pay the premium for one in mint condition.) PCjr heads - check this out: http://pws.chartermi.net/~mbbrutman/PCjr My contribution to classic computers .... Thanks, Mike