I just tried that and it did not work. Perhaps there is just too much resistance built up over the last 33 years.

But I did get the clock to work! I found that the ground is the little nub just to the left of the 12V connection. I just brushed into it and heard the clock start running. I left it hooked up and the clock kept good time during the time I had it powered up.

The nub is not marked. It just sticks out there, but it is making contact with the metal plate you were talking about. I guess I had to just go right to the source.

Looks like I need to take it all apart and clean everything so all the connections are once again good.

Thanks!