Electrpnic tachos again

[Firingonone]

While the tank was off my 1975 3 1/2 Strada to put in the new fuel tap diaphragm I decided to see if anything could be done for my electronic tachos erratic decidedly non linear performance .
Tracing the wires ,tucked up under the frame I found this

IMG_20250213_135447_454.jpg (50.86 KiB) Viewed 3270 times

It contained this corroded circuit board

IMG_20250213_133513_394.jpg (60.5 KiB) Viewed 3270 times

IMG_20250213_133624_757.jpg (51.55 KiB) Viewed 3270 times

I have had the bike over 15 years and before I resort to trying to adapt a chinese tacho can anyone tell me what it is ,and can it be Fixed?replaced or copied
Thanks

[George 350]

Hi,
As no one answered the question before, may I suggest that the circuit board may be one of the 'widgets' that used to be sold by NLM to allow the tacho to work on coils/transducers that didn't have the grey terminal for the tacho drive?
Never had one, but know that such things existed. The wires look far too good to be Italian!
Good luck,
George

[Firingonone]

Thanks, thats confirmed my worse fears!.
It also limits my options. I note in tutto gas vol 390 the conversion of the chinese tacho didn't work on CDI units without a dedicated lead which is my case.
I am not electronically minded but will see if someone can replicate this board as a starter or can any one help?
If anyone has a mechanical drive they can spare I would be very interested

[Firingonone]

Thanks, thats confirmed my worse fears!.
It also limits my options. I note in tutto gas vol 390 the conversion of the chinese tacho didn't work on CDI units without a dedicated lead which is my case.
I am not electronically minded but will see if someone can replicate this board as a starter or can any one help?
If anyone has a mechanical drive they can spare I would be very interested

[Ming]

My ’76 Strada had electronic tacho and one of those ”widgets”. They were not a complicated circuit and I know that there is a description circuit diagram and pcb design floating about somewhere on the net. A relativlt confident DIYer should be able to build one.

[Firingonone]

thanks again
I have been led to part 3 of Soren Hansens opus on youTube on Moto Morini ignition in 4 parts. This offers two circuit diagrams that can be home built for this problem . I will engage a "relatively confident DIYer" to build one as that is not me.
Who knows the tacho may not be the faulty part but if it is the at least I have the Chinese option.

[tony white]

For the relatively small effort involved, I'd give that board a good scrub both sides with a toothbrush and contact cleaner before giving up on it. Dirt and corrosion across the tracks could be enough to cause problems.

My electronic tacho was completely dead until I swapped out the trimpot on the internal board - corrosion of that trimpot looked to be the cause.

Tony

[Firingonone]

Thanks will give that a try first.

[Firingonone]

An update!
I had the widget repaired and now have a linear response to revving the engine but only to an indicated 5500rpm although it sounds more. I think I am going to have to open the tacho up to investigate further.
Any ideas?