Tach isn't working

[BigmanjbMOPAR]

For some reason my tach in my rallye cluster isn't working I tried it with the new msd box and direct to the coil neg. (Dash is partially out still). are they know to go bad or is there something I'm missing?

Having other issues too but haven't tried to troubleshoot them yet.

[Skdmark]

Did you have a good ground to the tach case?

If you have the tach out, you might want to consider upgrading the internals. RT-Eng has 2 kits available.
https://www.rt-eng.com/index.php/RTE_67-74_Tach_kit.html
https://www.rt-eng.com/index.php/67-74_Tach_Board_with_Calibrator_Built_In.html

[JP426]

I have heard that the factory tach will not work with a MSD box without a separate MSD tach adapter. Apparently it doesn't get the correct signal.

[dodj]

You need an MSD  adapter

https://www.holley.com/products/gauges_and_gauge_accessories/tach_adapters/parts/8920