tach input protection circuit for Zeitronix
RJ's Zeitronix ZT-2 was damaged at Sebring by a high voltage pulse on the tach input wire. This is easy to do if you are using CD ignition and you connect to the wrong terminal. I recently lent my ZT-2 to a couple of friends to help them tune their Webers and I built a little protection circuit to shunt high voltages to ground instead of going into the Zeitronix. I tested it on the bench and it worked fine on a car with a Pertronix pickup. It then worked fine on the car with points after the value of the resistors was increased to 20K.
Here is a module that I made for RJ. Yellow wire to ignition, green wire to Zeitronix tach input and black wire to ground. I will post the circuit if anyone is interested.
76 Suzuki GT500
2011 Jaguar XKR
A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
Last edited by alfaparticle; 06-05-2016 at 08:41 AM.