Re: Tach for 70 AMX

[Tom Jennings <tomj@xxxxxxx>]

The old ones go in series with the tach.

Inside the tach instrument, is a very ordinary D'arsonval meter  
movement. It is trivial to build a modern, cheap, simple electronic  
circuit that would make it a "voltage" type tach. An input filter  
network driving a NE555 type timer chip in monostable mode pumping a  
capacitor integrator and a trimpot to calibrate and it'll be as  
stable and accurate as any analog tach (and work on a 6 or 8). I plan  
on doing this with my 70 Hornet tach when I get around to it, this  
winter.

IC tach circuits were a classic 'build it' project when I was in high  
school in the early 1970's. Making it fit into the tach housing is  
the only real effort, and that's just careful hobbiest construction.  
Making a little outboard box would be easier. It won't "be stock" but  
personally I have no care for that.

I'll post a how-to when I do it.


On Nov 21, 2005, at 5:59 PM, Todd Tomason wrote:

> I've been working with an electrical engineer that designs and  
> manufactures
> replacement circuit boards for tachs.  He's been doing mainly Mopar  
> so far,
> but is trying to branch out.  I sent him a Tic-Toc-Tach for a 71-74
> Javelin/AMX to take a look at, and he found out that it uses the  
> same board
> and clock module as the Mopars.  His website is
> http://www.realtimeengineering.com/, but he hasn't added the AMC  
> info yet.
>
> Someone sent him a tach for a 70 AMX and he's trying to figure out  
> how it's
> connected to the car.  He said after looking at it that it might  
> connect in
> series with the coil.  Is anyone familiar with these?  I'd like to  
> get him
> pointed in the right direction.  A wiring diagram would also be  
> helpful.
>
> Thanks,
>
> Todd