Thanks I wasn't sure if it was mechanical or electronic. I will check that out . Looks like a little diffelcult to accessWelcome to TBN. You could start by disconnecting the tach cable and see if it's broken internally. There's a cable inside the sheath you see. Sometimes they break. If you know the length many auto parts stores sell replacements.
Most tachs from that era on the Japanese tractors were from Nippon-Sieki from the motor sports realm. Just modified for the gauge paper print. YT has a few clever ways to open them up, repair and reset the chrome original ring back in place.Thanks I wasn't sure if it was mechanical or electronic. I will check that out . Looks like a little diffelcult to access