[padgett]

Said before but "in general" a single wire tach will not work with a transistor ignition. In the figures below the single wire tach is what is to the right of point "D" and needs a strong trigger. The transistor section to the left of point "D" is an amplifier for a lesser signal. Which circuit you use depends on whether the coil is above or below the "coil ter".

I have ordered a circuit board from eBay but the vendor has two units and when received will know which is which.

Back in the day I could build a separate module for the transistor front end to connect between a transistor ignition and a single wire (usually hood) tach.