A Coworker need his tacho and hour meter fixed for his tractor - unfortunately the main IC in the circuit was dead and come from some obscure company in Hungary so unable to repair the device I redesigned the circuit based around an LM2917. The hour meter required a two phase signal to drive it I made a simple oscilator from a CMOS inverter and inverted an output to givethe appropriate 2 phase signal to drive the clock motor via a couple of small signal transistors. To fit in the back of the tacho housing I etched my own board and used SMD parts. The free running oscilator doesnot make forthe most stable clock butis suitable for a relative hour meter on the tractor.
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