My el-cheapo 5200 trak-ball arrived last night (with bonus 5200, power pack, and controller -- all to be used for parts).

I plugged the trak-ball in and....it worked! Well, the buttons all work great, including the keypad and Start|Pause|Reset. The ball did sense all four directions, but it moved very roughly.

So I opened the case and cleaned off the bearings and the ball itself. The corner bearing was the worst of the lot, with rust and crud galore. I cleaned it up, and it does spin very nicely now, but it's still got a rough surface so that's still causing occasional problems. I may replace it once I've cleaned up the rest of the unit and made sure everything else is in good order.

Still, it was very nice to play Centipede with true trak-ball motion last night!