The Restoration of PRRROWL
TIGER # B382000221
An Article by John Crawley
March, 2001
Page 26
Tachometer Fix
The tack in my TIGER would not work when I started the engine for the first time. I got out the "Shop Notes and followed the steps that were outlined. The transistors tested as O.K. and were not the problem. After a bit of testing I came across a weak spot in the design of the instrument that proved to be the trouble with my particular tach. The problem is once again the epitome of many of the gremlins in English electronics — grounding. You may think that connecting the ground wire to the posts on the back of tack case would ensure that you have grounded the instrument. This is not necessarily so. The ground problem in this instance is internal. When you take the tach apart you will find the round head of a rivet just above the positive terminal for the power supply. This rivet is the back of the negative or ground terminal. The rivet holds a thin brass jumper that leads to the nearest threaded hole that the case bolts to. The problem is in the connection between the case and the thin brass strip. The surface of the brass can become tarnished and contact with the screw is marginal. To fix the problem solder a piece of wire on to the front of the rivet and route the wire through a new hole that you drill in the back of the case. Terminate with a ring that fits over the threaded post soldered on the back of the Tach case. The original black ground wire may now be directly connected to the new ground wire when the tach is in place.
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