LM2917 Tachometer for V12

Alex, did you eventually get a tacho that works ? I have the same problem, checked all the resistors and capacitors and all seems ok so i suspect the 'unknown' TI chip is gone.

There were 5 wires and 6 wires OPUS systems. The 5 wires picked up the tacho signal directly from the '-' of the coil through a 6.8K Lucas resistor .

I am now using a Petronix ignition system, it works very well

Rui

Wow, this is an old thread! I'm sorry I've only just seen this. Yes I did get it to work using the circuit attached to post #32 but with a couple of changes. I said earlier in the thread that the 47k resistor was wrong, it should read 4.7k, and I also changed the 0.022u cap for something a little bigger, but can't remember exactly what now - it was three years ago!

I guess you've got yours working now but my system is not the OPUS, I changed it to the later AB14 amplifier used on HE engines. One day I plan to put it back to original in spite of its unreliability, so I'll have to wait and see if it still works after that.