It seems I left the most important part of this mod almost till last: the PBI itself. I'm following the (amended) instructions by Bob Wooley (PBI for 1200XL), but it took me a week to find a suitable bracket for mounting the 50 way Centronics connector to the back of the motherboard. I picked up all kinds of cheap metal brackets from hardware stores, but ironically enough the suitable parts were eventually found in the spares box right here at home. I absolutely did not want to mount the connector to the back of the case; I wanted it to rise from the back of the PCB for the sake of easy maintenance and case cleaning (just in case that 1200XL goes yellow in the future). What I eventually found were two 90 degree steel brackets which turned out to be just the right size.

Here are a few views of the completed connector:

I basically drilled two holes in the motherboard (I had to move some of the power supply traces on the right hand side) and bolted the brackets in place. It was rather a tight squeeze, and there isn't even room for washers on the screws holding the connector to the upright supports.

Still, it's solid enough and I'm happy that it won't place too much twisting strain on the board. The plan is for the ribbon cable itself to come off the back of the connector, then snake back under itself around the back edge of the board around to the underneath, where most of the connections will head for the underside of the CPU socket.

Getting the connector to line up with the pre-cut aperture in the back of the case was tricky, but I widened the holes in the brackets sufficiently to allow some adjustment. I've tested the IDC connector on the back of the finished unit and it feels nice and sturdy.

In the final entry, I'll briefly cover internal BASIC, as well as wiring up the PBI.