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...open up your Veglia and close it back again...

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After some 25,000 km of service my white faced, nice, foggy Veglia tach decided not to put up with being rattled around any longer and quit it's duty. At first it started acting up, displaying from 0-9000 rpm @will, just so that it could, after a few hundred kilometers more, settle for zero. I already it wrote it off for good, as, during one of my last rides, it winked at me. Cheeky! :bbblll: Of course, i just couldn't leave it like that. Had to see what's inside. :luigi:


Already as the tach started acting up I read about how it is nearly impossible to open up one of these for repairs, and how it is even more difficult to close it afterwards.


So I came up with alternative approach. No guarantees that you are going to like it though. :oldgit:


To start with remove the tach from the bike. If you own a Le Mans it is easiest done by unscrewing the three screws holding the instruments unit to the bike, disconnecting speedo cable, removing the odometer reset knob ("wrong threaded" - turn "wrong way" to unscrew) and flipping the entire unit upside down, back facing you. That way you get good access to the screws holding the tach in it's hole, and minimize the danger of loosing the small plastic washers underneath those screws.


Once you are done with that, you can pull the tach out of it's hole. At this point you can pull off the three wires (red = +12V, black = ground and yellow = signal) connecting the bike with the tach, pull out the small light bulb out of it's hole. There is an extra grounding wire attached to the instrument body by one of the mounting studs. You'll need to unscrew the stud, in the process of you will likely get it at least "wiggly" if not broken. Ignore that for the moment, as it is not as bad as it sounds. There is a theory out there that actually this wire and it's good connection with the instrument's body is responsible for it's proper functioning. Wrong!!! It has no connection whatsoever to the electronics, and it only makes the little light bulb work.


Now that you have the thing on your desk you can start contemplating how to open it.




I was pretty much discouraged by the description of the attempt to remove the decorative bezel of the top, so I decided to cut the tach in half. Savagery, hey!? :blink: I used Dremel with one of these small, metal cutting, black discs. I placed the Dremel in a vice, vertically towards a workbench surface. I placed the instrument face down (glass down) on an old Conrad Electronics catalog. Cutting right down the middle seems to be a good idea, so I ripped some pages out of the catalog, until I had the instrument in the precise position for cutting. Start the Dremel, and spin the instrument against it.




Now it's open. Make a mark on the body, so you can install the dial properly oriented later on (i.e. knowing which way is "south"). To remove the pointer use a kitchen fork, and pry the pointer gently off the axis. Remove the two black screws and the dial plate will come off too. You'll have following parts in your hands:

- top half of the instrument with the glass firmly attached

- one plexiglass ring situated bellow the glass. It's purpose is distribute the light from the little light bulb evenly across the tach's face.

- one bleached pointer

- one aluminium dial plate (opaque, hence the plexiglass ring)

- bottom half of the instrument with the electromechanics attached to it.


So how does the silly thing work? The "thing" is based on a CS8190, a "Precision Air-Core Tach/Speedo Driver with Return to Zero". In essence it is a frequency to voltage converter, one sine, one cosine voltage on it's outputs, holding the meter in balance at the certain position. Read the PDF for more info.




You may want to go on with disassembly further than that, but at this stage I noticed that one of the hair-thin wires of the "air-core meter" was not attached to one of the four studs (four shiny points in the picture), so I soldered it back, placed the pointer back on, and connected the tach back to the bike for a test. Worked!!!


Here is how to put it all back together again:


1. Screw the dial plate back on

2. Put the pointer back in place, and align it with 0.

3. Thoroughly wash/clean the glass and place the top half of the tach glass down on your desk

4. Throw the plexiglass ring back in the "top half"

5. Put the bottom half of the tach on the top half.

6. Give it a once-around with a silver duct tape. Don't give it twice-around, because it will not fit back in it's place.


Finished. Connect to the bike and check if it is working. If not, undoing the duck-tape is not excessively expensive, so you may go at it again.


Mine works! Even the fog is back where it was. As happy as a clam. ^_^

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:P:P This is one of the greatest how-to's I think I have ever read. Kevin Cameron would be proud. Good timing, as well- my tach just crapped out last week. You might be on to something, here! :bier:
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  • 4 weeks later...

Let me add that the earlier Veglias found on the short frame KRs are built up different. Different electronics. They usually just stop working and in most cases it's not because of a broken connection or wire.


And: the internals of a Tach or Speedo might be magnetic, so make sure that no metal chips and flakes get inside.



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Outstanding write-up. :notworthy:


The cut-n-duct-tape beats the living stuffing out of the way I did it 3 years ago (thru the bezel) in terms of quick & easy:




But will duct tape go the distance? :huh2:


Enquiring minds (well, you know. . .)


You can buy aluminum tape at some hardware stores. Very thin aluminum (not foil) with an adhesive backing. 3M product I believe. Also copper tape, smooth or embossed. More expensive. Way more expensive. The metal will do it's job but I'm unsure about the adhesive when it gets warm out. It's kind of weird thinking about these things being products but they're out there. Along with steel wool, you can buy lead wool. We used to stuff it in the shielding gaps to block the radiation on a linear accelerator I worked on many years ago.

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But will duct tape go the distance? :huh2:


Well, time will tell, and if not time, I will... :oldgit:

So far, as far as mechanical properties are concerned (aesthetics aside), I had only positive experience with "the tape". Amongst other things I've been repairing ripped sails with it, and they would last through the summer, not minding water, wind, salt, temperature, nor radiation. And even when (or rather if :huh:, as I don't remember a single incidence) it would come off, it is cheap to replace. :P


According to "the original design" I drilled small holes above and bellow cutting line, thinking of inserting a thin sheet of metal inside the cup and soldering the top and bottom halves through the holes to the metal sheet. But rummaging through my supplies I came across a roll of duct tape, and the little devil on my shoulder murmured: "Take it, just take it"! sm1_694.gif


Many things speak for the tape - cheap, easy to handle, no tooling required, comes off if need be, etc. Wikipedia on Duct (Gaffer) tape

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  • 7 years later...

Well, thanks to Guzzi2go i was able to attack and repair my veglia tach too. Here are a few notes and pics...


Cutting it open took all my courage but was the easy part.





Once open and looking at the guts i figured the "hair" wires in the coil windings were probably broken. The 2 connections on the black wires on the circuit board showed no continuity... ends up it should read around 56.5 ohms.



I unsoldered them (they looked like the easiest to get to), unhooked the 3 connectors and turned the 2 plastic clips (yellow and brown you see there in the middle) to get the IC board out of the way.


I then seperated the shaft assembly from the base.

DISCLAIMER: To get it all apart and get the coil out I ended up breaking the tiny end of the shaft that is held by a small copper ring pressed onto it. It prevents the assembly from pulling out upwards from the base. Once reassembled this did not seem fatal - but is clearly not ideal. Not easy to get around in my opinion.




I bended the tiny clips aside and got the coil free to find the broken wire underneath. I unwraped it just enough to resolder it in place (don't forget to burn off the varnish from the wire with a lighter to get a good contact).


Reassembled it : a bit of a delicate PITA - but it now works!




I applied silicone to the casing to seal and hold it, but had to remove the outer bead to make it fit in the instrument panel hole so i added a wrap of duct tape too.


Overall i'm happy it now works and cost me 0$, but the seal between the gauge and lower plastic cover is not as tight as it was... Notice the gap between the 2 halfs in the pic - i wanted to account for thickness of cut but that was not the best. Maybe would be better to rivet them in place with a back-plate or something. Oh well, next time :)


Overall it's fixed!

Hopefully this helps the next guy.

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  • 3 years later...

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