Quote:
Originally Posted by DonSteve
I too have a blown tacho (I think), it was a long time since this posting but can you remember how you diagnosed/fixed it?
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On the Circuit board behind the clock on mine there were two Charred components e.g a Diode and a Resister close together.
I had an old 1n4004 diode
https://www.ebay.com/itm/10-PCS-1N40...8AAOSwPK1ZTq33
in my bits box and used that but you can use a modern equivalent.
Then also replace the Resistor which I think a 30 ohm will do the trick.
Remember the Diode is directional so MUST be soldered the correct way round so if there are any markings left on the Diode on the board take a Photo with your phone.The resistor isn't so it doesn't matter.
If you are lucky like I was these two components acted as a Fuse and blew saving the rest of the circuitry.
Once all done I had to fiddle around with the Tacho needle to set to right.
Tip:I used a kitchen fork to keep taking the Need off and putting it back on the Tacho with the engine running until I go close to the correct position.Once set and after a few miles the Tacho settled back to being ok
Note:The cause of the Tacho failure was,"Over-Voltage" caused by a failing Regulator/Rectifier.Before repairing the Tacho I replaced the failed one with an Updated Mosfet version as per this page I made,
https://cx500.000webhostapp.com/Mosf...sfetUniRR.html