Tachometer Issue

[luhbo]

I had mine open these days. I couldn't see anything obviously broken, so I had to give up and just closed it again. Time will bring a new used one I hope.

 

At least two things may be of interest to some of you:

 

- you can't remove the mass connector from the housing! As soon as you try to open the nut the whole bolt will come loose. If anybdy wants to remove the tach, just cut the black minus wire that goes to the bolt and resolder or reclamp it later. And open all four nuts of the cover - remove the cover - remove the connectors and then push the tach or S-meter out through the sealing ring.

 

- there is no internal connection between the tachometer parts and the housing! All three connectors are internaly wired through to the PCB. A loose cable is most unlikely!

 

What could it be then? As someone has already said, there are about ten discrete parts, resistors, caps, a trimmer, and one IC. These parts normaly don't fail.

 

One theory is, that the 4W bulb inside is heating the parts. Not very much but maybe enough for the caps to dry out and die.

 

Can anybody help with a data-sheet for this SL494 with *** 14 *** pins? Google finds only the version with 16 pins, or the actual part TL494, also with 16.

 

I think if I could compare the 14 with the actual 16 pin version then repairing a tach could be easy. The TL494 costs 20 cent!

 

Hubert

[belfastguzzi]

It's that pesky dain bramage again. <_ but i pretty sure posted photos at one point src="%7B___base_url___%7D/uploads/emoticons/default_knownothing.gif" alt=":huh2:">

 

I remember shots of the studs & everything. . . . . Or am I mis-remembering visions etched in my mind of my own excursion into the rarified inner landscapes of Veglia Borletti??

 

A remembery is a terrible thing to lose.

This is the thread that I remember, but whichever posts they were, the pics have gone in all these threads (presumably in the Great Cull of 2006).

 

http://www.v11lemans.com/forums/index.php?...c=2983&st=0

[luhbo]

Thank you for the link. The stepper driven tach looks interesting, but all what a quick search could bring up was very expensive!

 

The rest of the article, hm. They say the additional cable could cure their problems. Probably we're speaking about different tachometers here. The european version of the Veglia has no connection between posts and tach PCB. The black cable going to one post is needed to ground the bulb, not more. If it gets loose the tach goes dark. Shows you this way that it's time to get home

 

Hubert

[Paul Minnaert]

Hi luhbo, someelse was looking for the same info:

http://www.mikrocontroller.net/forum/read-1-181263.html

[Guest Gary Cheek]

I just repaired the tach on my 2001 V11. Unlike the ground issues on this unit the problem was the clock spring type flexible conductor that goes to the driven needle. There are two helical hair springs. One of them is actually a spring the other is a phosphor bronze conductor. The bronze,copper color conductor on mine had broken just outside the soldered connection. I merely put a dab of rosin on it and re-soldered. Since this is a minimum tension area the slight shortening will have little influence on the accuracy. Not like Veglia are lab sandards anyhow. If I see a need I will consider making a fixture to unroll and re-roll the bezel's hem in my lathe. Should make for a barely detectable repair.

 

While I was at it I brazed the two staked in sorry excuse for stus POS that the Veglia folks had in there, a thin coat of flat white Krylon and probably paint the needle BLACK while it is apart. Will re-hem the bezel and have her running tonight.

 

 

Luhbo , my tach looks to be the same as you described. Take a look at the forward balance "spring" (actually a conductor)

 

So,

If you had yours apart and found nothing wrong, take a look at the helical springs. My bike only has 12K on it so I may be in there again.

 

BTW if anyone has or knows of any Veglia DOA stuff that has been given up on I would be interested in buying a few speedos and tachs. Any years any models.

[luhbo]

Hi luhbo, someelse was looking for the same info:

http://www.mikrocontroller.net/forum/read-1-181263.html

 

Yep, seems to be hard to find this one! Thank's anyway.

 

Hubert

[callison]

Can anybody help with a data-sheet for this SL494 with *** 14 *** pins? Google finds only the version with 16 pins, or the actual part TL494, also with 16.

 

Hubert

 

I've been keepoing my eyes open for about three years for the 14 pin variety. Even a spec sheet with pinout would allow for a socket substitution kit, but alas, I've found nothing...

[luhbo]

....

So,

If you had yours apart and found nothing wrong, take a look at the helical springs. My bike only has 12K on it so I may be in there again.

 

BTW if anyone has or knows of any Veglia DOA stuff that has been given up on I would be interested in buying a few speedos and tachs. Any years any models.

 

Gary,

 

thank you for the hints. On mine these were ok. Anyway the circuit seemed to be broken. Instead of just resolder all the joints I completely disassembled the whole thing, only to find that even the thin wire was ok over its entire length. Rewiring the coil has something of Zen, I tell you!

 

So the funny thing now is that that the tach now works again.

 

So much about the theory with the dried caps. Maybe the fault on mine were just one or more weak solder points, who knows. Or it is indeed a problem with the connectors.

 

Wait a bit and I will post some pics from the one with the definitely f#%§ed up electronics. This one goes up to 11000 as soon as it gets the first impulses from the ecu.

 

In the meantime you can look what Cliff found out about what is send to the tach.

 

Hubert

[luhbo]

Some might have been waiting for the promissed pictures. Here they come:

 

The conductor springs.

 

The coil

 

PCB

 

Back of PCB

 

PCB roughly laid onto the mechanic unit

 

By turning the small poti one can adjust the tach. Maybe that a drilled hole will give access to it.

 

You see, really nothing that should brake or go wrong besides the springs that are looking to be quite prone to vibration induced damage.

 

Hubert

[luhbo]

That's how a freshly painted needle looks:

 

[Guest Gary Cheek]

That's how a freshly painted needle looks:

 

 

Thanks for the excellent photos! The "spring I was referring to is the rear, finer of the two. Mine was broken about 1 MM from the mouting post. Being more practical than purist I painted the needle flat black. I ride the bike to work every day and it sits outside almost all of the time summer and winter. The needle was nearly white after the first year. Aside from needed repair to the tach I would have had to repaint the needle anyhow.

[luhbo]

Thanks for the excellent photos! The "spring I was referring to is the rear, finer of the two. Mine was broken about 1 MM from the mouting post. Being more practical than purist I painted the needle flat black. I ride the bike to work every day and it sits outside almost all of the time summer and winter. The needle was nearly white after the first year. Aside from needed repair to the tach I would have had to repaint the needle anyhow.

 

I thought the speed-o-meter looks as if it must get also opened sooner or later because of the missaligned digits. Then this pointer will get its new coat. If I do it this winter I have a good chance that the colors will match.

While I was at it I changed the bulbs to green ones (laquered them) to add some more color. The all black times I let behind me. On my previous bikes everything looking a bit rotten got a black repaint, but now, getting older, at least the bike should keep as much as possible of it's shinyness.

 

Hubert

[Guest Gary Cheek]

I thought the speed-o-meter looks as if it must get also opened sooner or later because of the missaligned digits. Then this pointer will get its new coat. If I do it this winter I have a good chance that the colors will match.

While I was at it I changed the bulbs to green ones (laquered them) to add some more color. The all black times I let behind me. On my previous bikes everything looking a bit rotten got a black repaint, but now, getting older, at least the bike should keep as much as possible of it's shinyness.

 

Hubert

 

Sounds good to me. The "shine" is pretty much gone from my "01. I bought it from Ebay a few years ago with only 2500 miles on the clock. It was in a salt water flood in Maryland and totalled by the insurer. It has been my utility bike .

 

A note on the instrument lights. Mouser Electronics and some other electronics firms sell LED replacements for the bayonet base bulbs in many colors. They only draw 30 to 60 mA and put out good light. Comared to the 180 or so mA that the incandescents will draw.

 

Thanks again for the photos!

[guzzidog11]

Since I started this thread, I thought I would give it a post-mortem. I found some time over the weekend to pull out the tach assembly and probe around inside. As suspected, what I found was a loose case stud that allowed the ground wire to flop around a bit and a loose connection on one of the other wires on the back of the unit. I tightened the case stud, reattached the other connector and voila! everything worked fine. There were a few "Italian" moments in the process. While I was testing things, the light on my speedometer quit working, which required taking everything apart again. While replacing the speedo light, the fuse blew. I replaced the fuse and everthing is working fine...so far.

 

Thanks for all of your suggestions and the information from the forum. It's nice to have my baby fully functional again.

[Guest Gary Cheek]

Hello dog,

 

I think our tachs are a bit different. There are no grounds under the poor excuses for case studs on this tach. The case studs were of course loose also. In my case I TIG welded the buggers in place and used an external star ;pck washer under the stud extension. It will not come loose again. Next Guzzi I buy will see the instruments disassembled and the updates completed without waiting for them to fail.