Hello,
I just checked the continuity on both of the DIN / Merit accessory sockets that I have removed from the bike.  On both sockets the positive blade has great continuity to the inner receiver of the socket, however the negative blade has no continuity to the socket's barrel that would make contact with the negative fingers of any
plug-in device.  Both sockets are the same which is really odd to see both fail in this manner.

Has anyone else encountered this problem?

Thanks!
Jim

Yeah, the connection from the terminal on the outside to the metal bits on the interior.  I had that problem on the accessory outlet in the coil cover on my K75RT. It made connecting my trickle charger sort of dodgy.

If I remember right, there is a strip of metal that runs down the side of the socket from the connector that goes under another piece on the side of the socket.  It seems like the electrical connection is simply the mechanical contact between the two parts.  Over the years I think that vibration opens up the fit between the parts and the electrical connection becomes intermittent.  

It's been a long time since I repaired mine, but I recall soldering the parts together.  It wasn't all that hard, it's just that the parts need a bit of heating to get the solder to flow.  So far, the repair has held up for over 4 years.

I have also seen this on the negative side, in my case I cleaned it and managed to get a connection.