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There have been a few PCBs with a plating through problem, I've just received 2.
This is what Piet has said about it;


The -ve voltage pad that the screw terminal solders to is not plated through to the ground plane on the top of the board.

Root Cause:

The problem is related to a small batch (<16) of motherboards with the production code M120726D only and need to be reworked. (Production code is on the board backside)


Rework instructions

An inverted omega shaped solid wire to be solder on top pad with extra, but not excessive, solder. Then install terminal block preference is to solder the positive pin first. On the backside form solid wire around the negative pin and solder with sufficient solder.

Corrective Action:

PMV to contact manufacturer to check reason for deviation of certified process. When required adapt board design to avoid future problems.

My solution was somewhat simpler. I don't use the fiddly individual connectors, I use terminal blocks so I just ran a wire from the incoming negative round to one of the ground connections on the in/out side.

Thanks Ecca.

Good tip. Just checked the one I am in the process of building and it was from that batch number and on checking had the plating through problem. You have probably saved me a lot of time and grief trying to troubleshoot it later on !!

Regards, Dave

Good.
In fact it was Roger Cook who first discovered it after scratching his head for a while and he then told Piet and myself about it.