Tachometer not working '71 911

[kandhmfg]

My tach is not functioning. It is the original tach as far as I could tell, the car didnt run when I bought it so I have no idea if it worked before I sent it out to N. Hollywood speedometer had them clean it up, check it out and reface it, etc. several months ago.

I know I have the tach hooked up properly in the dash, just making sure that the correct connection for the signal is the tab on the side of the distributor. It was a Marelli distributor when I got the car which has been swapped for a Bosch unit (does that matter?). The purple and black wire runs from the distributor up to the tach for the signal, again I have a good ground, I have power to the tach 12v. I have a faint signal from the distributor through the purple/black wire. Anyone know what the signal strength should be for this tach to work? Could that be the problem?

I am having a pro check it out as well and it appears all should work. I am sending the tach out to test it is working internally again. However, wondering if maybe there is something I am missing about the signal travel in between the distributor and the tach itself? Was there anything in line between those two points that could go bad?

Any thoughts are appreciated.

Thanks,

Erik

Gratuitous car pic