Tachometer Sending Unit

The tach in my car has never worked since I bought the car.
I was checking the wiring yesterday and found that there are 3 wires on the sending unit, and one bare screw.
When I turned the bare screw the tach needle went all the way around to the other side of the tach.
When I turned it back, the needle went back to zero.
Is this an adjusting screw?
No matter how I tried I could not get the tach to function. It was either on zero or maxed out.
Do you think the electronic board inside is trashed?
I’ve installed electronic ignition. Would the electronic ignition have affected it?
I don’t want to have to buy the new electronic board if I don’t need it.

The tach in my car has never worked since I bought the car.
I was checking the wiring yesterday and found that there are 3 wires on the sending unit, and one bare screw.
When I turned the bare screw the tach needle went all the way around to the other side of the tach.
When I turned it back, the needle went back to zero.
Is this an adjusting screw?
No matter how I tried I could not get the tach to function. It was either on zero or maxed out.
Do you think the electronic board inside is trashed?
I've installed electronic ignition. Would the electronic ignition have affected it?
I don't want to have to buy the new electronic board if I don't need it.