Electronic tacho 78 2H9 issues

[melbxs]

Some deep discussion here:

http://www.benefiscal.co.uk/forum/index.php?topic=7926.15

Need to chase Miti up to see what his final findings were.

[Christian Raith]

Tacho runs off the alternator so better check the connectors to that, if they are all ok make sure that none of the windings are wearing through and getting grounded.
I had the same problem and it turned out to be the alternator.
Mechanical tolerances on the windings are quite close.

[Aussiexs11]

Ok,
I am of the understanding the tacho on my 78 2H9 is electronic.
Ive noticed a couple of weird things on mine.
Needle sits about 1800rpm mark at standstill.
When engine running and reving, it frees and seems to indocate accurately (from ear and memory) to around 5000.
On the road, once the bike is being "worked in a spirited manner", and I know its getting up there, the reading I get holds and rises slowly from 5000 to 6000 and I know its being worked a little harder than that!!
So, do I have a bent inner workings, is there a resisitor or some electronic device that could be blown /non functioning or is the whole tacho stuffed?
The fuel guage works well, thats a bonus!
Its a square tacho unit.
can anyone help , or does anyone have a spare that works and has also a working fuel guage too.
I did swap this tacho out a while ago as my last one was "bouncing" a little too much and the fuel guauge stopped working. I no longer have it of course!
Your thoughts........Grant