I picked up this engine analyser.
Some functions (like battery voltage) worked, and other (like tach and dwell) did not work. I suspected that this would be the case, so naturally I opened it up.
Aha, look at that! Dried out electrolytic residue. Blown caps. So two 330uF caps are in my future.
Turning it over, more carnage - some of the trace has actually peeled away from the PCB!
Because the damage to the trace is so extensive, rather than trying to repair it, I'm simply going to run bridge wires from the most convenient component terminals.
Stay tuned!