The tach in my '73 was working intermittently. Sometimes I would have to tap on the front of the gauge to wake it up, but now it doesn't move at all. All the wires at the coil are connected and look good. The last time it worked it died after reaching 2500 rpms . Is it dead? Thanks!

Sounds more like a loose connection at the back of the tach itself. If it starts working after you tap on the tach, it sounds reasonable to me that something is loose in the tach itself. If it isn't a loose connection at the back of the tach, then it could be internal. Since you already ruled out the coil connections, there's only a couple more things it could be.