Tachometer not working at all.

[GoMangoBoys]

I wanted to follow up on this.  I was able to partially disassemble the gauge and spray some WD40 in the 2 places where the shaft spins.  I then just blew on it to try to clear out any contaminants.  It seems to have done the trick because the tach works perfectly now.  In summary, I replaced the electronic board with the RT-Eng board (including built-in calibration) and cleared contaminants from the movement.
https://www.youtube.com/watch?v=cdpy5OMfSss

[usraptor]

Glad to hear that you got it working correctly!!