I'm still dealing with getting my tach working properly with the Pertronix Ignitor 3 ignition module... While researching the problem in hopes of finding a solution, I ran across this semi-sorta DIY conversion...
Thought it might be useful for both Mangusta & Pantera owners...
http://www.dinoplex.org/tachoconversion/
MH
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...the tach in my car has something like that, before I got obsessed with this myself I sent the tach to PA speedometer to 'just have them restored' and it came back with a board hot-glued in like this...
The Dino circuit is simple (as are other '555 tach circuits), the surprising thing is that (with the billions of Veglia tachs) that the beautiful circuit board isn't immediately available on Ebay...Even, not a universal board. But I suppose one reason is that most people aren't going to have a function generator around to set the input frequency and calibrate needle/trim pot.... But making the circuit itself with a universal PCB could be simple...
The original Veglia circuit is not complicated either, just a couple transistors--but for me trying to test it (here in my Townhouse in Taiwan....) the issue was getting the 'trigger' to work--and trying to build an inductive amplifier (to take the frequency generator) should have been simple but failed me. So instead I took the Stepper Motor challenge. https://pantera.infopop.cc/top...93#19905352128593293
But another idea is to buy a cheap 2" 8krpm universal tach, make sure its triggering--then gut it and use the PCB or even the whole movement. Or (assuming the question is just the trigger), try that tach amplifier for $30...Lee
(oh, and in case the idea of transplanting a whole movement into the Veglia can is interesting, 2 things; (1) re-use the Veglia plastic bracket. (2) be patient beyond patient in fitting the Veglia needle onto the replacement shaft...the replacement motor is almost certainly bigger diameter, which then means either micro-surgery to drill out the female end on the needle and if break the 1mm or so drill bit into the needle, the only donor is another DeT gauge...)
Jon Haas (Pantera Electronics) has his own tach repair technique that is effective and less expensive than other repair methods.
Here is another solution that I used to correct the Tachometer readings on my TVR. It was reading double the actual RPM after a Pertronix module was fitted…
...Mike, I'm guessing that your problem is just that you need to adjust the Tach to the "V10" mode...probably just a tweak of the trim pot. You could try this on your Fiat piece and avoid one step under the dash...
Here is a schem taken from the reliable internet for the Veglia, it is simple. the only place that things go 'wrong' when mixed up on the ignition source is the filtering section there the south-west quadrant. Otherwise, the Q1 transistor pulses vaguely with every spark and pulls a current thru the meter, with a final gain set by the trim pot (R10). I think its possible that All veglia car tachs (no matter 4,6 or 9 cylinder) just twist the trim pot.
The Dinoplex circuit is simpler than it looks, the part internally has its own schmitt trigger to clean up the noise and react to the edge (not just the 'weight' of the spark, as the Veglia) and send a single pulse. (and something I'd be likely to do, the pin names on the CD14538 are a bit messed up...and come on, man, CMOS inputs should never be left floating... 
. But yup, its about $8 worth of parts....Lee
...that is so awesome, I have new hero in a "take my word for it..." engineering role model. And clearly filmed a long time ago, because now $750 million would not be considered expensive, esp for the government..."
https://en.wikipedia.org/wiki/Turbo_encabulator
And Mike, that is the beauty of trim pots...when I was in college, other guys were making measurements of their sacred transistors, drawing load lines, whatever and I would just grab a potentiometer and tune it till it worked. Maybe I have Italian blood somewhere there...
@leea so you're saying that even if i build the turboencabulator, I will still need to trim it's pots...? Ok, if I'm trimming pots I'll start with the Fiat tach and get a feel for it... Then try the REAL tach if i get foolishly overconfident... (seems inevitable).
Updates will follow...
MH
