Eight Easy Steps to Modify a Sprite Tachometer for Negative Ground

By Rob Garofalo

Originally published in the Austin-Healey Magazine, October 1991

Reprinted from the July issue of Oil Rag


Use a 50 watt pencil type soldering iron for removing and resoldering the internal wires, otherwise you will fry the board the components are mounted on. If you are not sure of yourself with soldering, find a buddy who has some experience in this area.

  1. Remove the rear cover.

  2. Behind the "10" and "15" numbers on the face of the tach, there are two wires. One is red and the other is black.

  3. Reverse the connections for the red and black wires.

  4. On the opposite side, behind the "60" and "65" numbers on the face of the tach, are a green wire and a tan colored resistor color-coded brown/black/ brown/silver.

  5. Remove the green wire from its post and remove one end of the resistor from the adjacent post.

  6. Resolder the green wire to the post where the resistor was connected and resolder the free end of the resistor to the post where the green wire was connected.

  7. Replace the cover and install the tach.

  8. If you had a buddy help you with the soldering, take him out to lunch or at least buy him a cup of coffee.

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