I've had several problems with these H851 connector blocks, but also dirty PCB contacts. It is a good habit to clean the contacts on the boards when rebuilding a machine. The old style H851 do not have plated holes, but metal buses. I have seen shorts and open contacts in H851 blocks. That is why I also made new PCB's for them. (And also to reproduce these blocks)Working on the second 8k core issue mentioned yesterday. I studied the prints until I convinced myself the problem is isolated to about 7 components on the G233 8k XY driver board. I pulled that board to inspect it knowing that it was possible the top block could also be at fault in connecting the lines to the core plane.