The Tachometer stopped and after analyzing the circuit decided to throw it away. I designed a new circuit and breadboarded it for testing. This is the power supply side.

A 555 Timer is used to drive the Meter Movement. The new board is the exact size and shape of the old board.

A Pulse Generator and Oscilloscope were used to calibrate the new circuit. It has been working perfectly since being installed in my Elan. Maybe someday I'll make a proper printed circuit board for it.