VDO Tach Upgrade, replacement for internal electronics Options

[914GT]

I'd like your comments about a project I'm working on. I have made a single integrated circuit design that replaces the old-technology internal VDO tach circuit. This is a more modern frequency-to-voltage converter (actually it's freq.-to-current) and it has several advantages over the original. Here are the key improvements:

• Internal voltage regulation and noise transient/surge protection
• Jumper selectable for 4, 6, and 8 cylinder engines
• Stable with wide temperature and supply voltage variations
• Better performance over stock units that have been modified for 6 or 8 cylinder engines (improved response, etc.)
• Simple calibration adjustment
• Wide range of input voltages, from standard points ignition and *should* work on most electronic ignitions (only needs a couple volts input signal)
• High input impedance

I've made a prototype circuit board to finalize the design for bench-test, and I want to lay out the final board next. I planned to design it to replace the original circuit board. This does make it harder to get at the cylinder selection or calibration. It would be nice to keep the board inside the tach and not have something mounted on the back. Would most people be willing to remove the bezel to attempt doing this? That's the hardest part, using a small screwdriver to carefully pry the rim off. The rest is pretty easy, small screwdriver and soldering iron are needed.

So, any interest in this? I'll build one for myself, but if this is something that would be popular it's possible for me to build up more as a kit. This would be for others like me who don't want an aftermarket tach and to keep it original-looking. Thanks for any suggestions.

[machina]

I'd be interested.

I went thru alot of trouble to extend the rpm range on my stock gauge, i really wanted to keep all the gauges with the silver point at the center.

Unfortunately I could not get the stock tach to work with my motor. Has CD box, tried the tach lead from that, the trigger lead from the dizzy, and the coil trigger but still couldn't get it to work.

Ended up getting this autometer at the local flaps, fit the hole and I have to say that the modern movement of the tach is really nice. Also has rev lite. Think the call it an air-core.

It would be great to have modern internals in the stock case.