Wiring in Electronic Tacho

Nsane1

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Hey All,

Have read many posts on here about wiring in a Tacho but this is my first time posting on here.
Building a 82 XS400 for a friend & have finished everything except the Tacho.

Converting to a Electronic Tacho bought on ebay.
I have tried 2 of the same tacho wiring it to the Coil -. First tacho couldn't get to move at all.
Bought another tacho & wired it with a 0.1mf cap> 1K resistor then T to ( 12V zener diode to ground +) & to tacho... As per the attached diagram & picture
With these pieces I got the tacho to move but at idle the needle sat at 2000, when reving the needle moves quite laggy & then when riding the needle jumped up to 4000 & when reving it moved to 2000.

I have used an oscilloscope & have pictures of the coil - attached
Plus pictures of the circuit & tacho etc.

Note: I have tried various capacitors, resistors & diodes but cant get it right.
Also I have tried spare car tachos I have in the same circuit & they seem to work fine without the extra circuit above. So Im thinking the tacho is just faulty but thought I would ask you all first.

Thank you kindly
 

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Hi, cool idea but post some more details of the taco’s you’ve boughtShould be able to pick up pulses like that.
Have you tried without the capacitor, just seems odd to have it in the circuit like that
Good luck
Gra
 
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