I have a 1980 Chevy shortbox. I installed a full gauge cluster from a dump truck that had the factory tach. I do not know the year of the dump truck. All the gauges work fine except the tach. When the engine is idling the needle sits pretty much where it should but it doesn't take much throttle and the needle buries itself as if I were bouncing the engine off the rev limiter. Just wondering if anyone out there knows what values I should be seeing on the multi meter if I were to test all the components on the circuit board? There is one resistor in particular that concerns me because its obviously gotten really hot and is burnt. Its hard to tell what colors the bands are supposed to be because they are discolored from getting burnt. I'd like to get this tach functioning properly again. Any help is greatly appreciated.