Tach Adapter Schematic/Diagram?

[Hardwyre]

Hey Z crowd. I just pick up a beautiful dust blue '76 Z last week and already have a dozen parts coming to clean her up (new carpet, power window kit, etc).

I have an MSD 6AL controller and Blaster 2 coil from a Chevy 383 stroker that I'm no longer using and figured, why not, throw it in the Z.

My research has brought me to understand that I need a tach adapter to make the 5v square wave from the MSD work with the 12v sine(?) wave needed for the tach and fuel injection of the Z.

The adapter MSD forums suggested was the 8910. They have about $50 for it. Thing is, if I could get a schematic for the adapter, or a similar circuit, I could simply build my own.

I've noticed there are some pretty electronic-savvy people on here, so I joined.

So I guess here is the short question: How do I convert the MSD 5v square wave to a 1976 Z's 12v sine wave? Also, do I even have the correct values? Thanks everyone.

[FastWoman]

The 280Z tach circuits are apparently proprietary and mysterious. I've opened up a '78 tach, and there are some key black-box components. I suspect nobody has a schematic, except for Nissan.

The trigger from a stock 280Z is not a clean 12VDC pulse, as it has some high voltage transients from the coil kickback. I don't know what voltages are necessary for the tach circuit to trigger. It might even trigger off of a 5VDC TTL pulse. If you need to convert 5VDC to 12VDC, just make a little comparator circuit. A 741 chip should do. Wire a potentiometer (maybe 10k) between +12 and GND, and wire the center tap to the - input on the 741. That pot is used to adjust your trigger voltage, and it should operate just fine over a very broad adjustment range. Then wire the 5VDC TTL pulse from the MSD to the + input of the 741, probably with a 10k resistor in series. Then wire the output of the 741 to the tach's signal post. Simple circuit -- nice beginner project.