speedo using mechanical and electronic drive

First coil I used was around 100 ohms which at 13v should pull enough current if the transistor is being driven hard enough which I assume it must be if it blows it up but after that I put another bc337 transistor in and tried a standard horn type relay coil and got the same result ....dead transistor..... I used a 2.7k base resistor only 200 ohms less than the diagram but I might try a trimpot and start at 5 or 4 k and see what happens. I might even put the cro from work on the signal and see what it looks like to see if its a 5v square wave like everyone says it should be.

 

Unless you can find it cheaper my original tacho now works with the v6 motor with the addition of this little board and I got it from whittakers in wagga wagga....80 bucks was a bit tall for this but it works...better than the 220 I got as a quote from a place here in brisbane ...... 4 wire connections 12+ red 12v- black 5v signal in brown 12v signal out blue

up here in queensland the exact sensor everyone uses I found at a speedo shop was 105 all day to anyone
And the original speedo now works with this setup on the gearbox ......a angled drive and a 2 pulse signal generator and custom speedo cable