Weird Tach Behaviour

[Anonymous]

That would be great . My e-mail is jeremiah_r18@hotmail.com

[Anonymous]

Just one last question, the capacitors listed on the ELFA site list them as
3,3uF/50V is that the same as 3.3uF/50V?

[kz]

Hi JD!

I am happy that I scanned the capacitors for you.

I scanned the replaced capacitors for and E-mailed them to you, after I scanned them I saw that the small one of the capacitors is 33uF and not 3.3uF, as both me and the salesman at Elfa thought (the number are really small)

Please look close at the scanned JPEG:s I mailed to you.

So the stock number I provided for the 3,3 uF should be replaced by a 33 uF capacitor

I will bye a new one; this could maybe be the reason for my reaming error.

The capacitors in original are 1 off 33uF, 25V, 85 degrees and 1 off 4.7uF 25V, 85 degrees.

The one I bought from Elfa goes to 50V but that doesn?t matter.

Edited 2002-08-10
RIGHT CAPACITOR ELFA PRODUCT CODES ARE 67-003-63, 33 uF AND 64-013-46 4.7 uF

[Anonymous]

I think i gave you the wrong e-mail address, could you please send the photos to this address jeremiah_r18@hotmail.com
Much appreciated

[moto_dan]

Would you send me the scanned information about the tach?

KZ,
Would you mind emailing me the scanned information about the tach problem. Sure would appreciate it.
moto_dan@yahoo.com

[kz]

Now I am confused

I bought the correct capacitor and soldered it in place.

Now the tacho has start to bounce again in a different way than before and never shows more than 7000 rpm.

So, did I destroy something because I soldered in the wrong capacitor or do I touch something during mounting and dismounting and it wasn?t the capacitor in the first place?????

I really have to rig up the tacho with a signal generator for finding this annoying error.

If you come up with something please let me know.

[kz]

I now have rigged the tacho with a signal generator and it runs like a dream on the bench, from 0 - 12.500 rpm fast changes and slow changes.

The value the tacho shows also corresponds to the supplied frequency.

But...

As soon as I mount it in the bike the new type of bounce is back.

I measured the signal from the coil (brown lead) and 12V mains (orange + and white -).

The signals look as I like them to look, but I didn?t measure the coil signal up to more then approx. 4000 rpm, because I don?t want to be hostile to my engine by revving it up to 9000 rpm in neutral and then adjust the trigging signal on the oscilloscope.....

I really lost the thread now and do not know there to look next, at the same time it is a little bit tiring mounting and dismounting the tacho....

JD, I never should have changed that capacitor to the correct one.

Anyone who has any clue is welcome Hap? JD?

JUST HATE TO GIVE UP! :twisted:

P.S Did you get your jpegs Moto_Man and JD?

[Anonymous]

It seems to me that your tacho is fine, if it works on the bench. Your signal is also good up to 4000 rpm.
The signal therefore is changing above 4000 rpm. The other change that has occurred is that your bike has aged, i.e. new bikes don't do this. Something is probably breaking down.
So, there are 2 possible sources for the problem : the signal OR the 12V supply to the instrument.
If the signal is the problem, the fault could lie within the ignition coil or at the ignition trigger. Could you take a signal from the other coil to eliminate this?
Or, if you have a 12V problem, is there a fault with the voltage regulator on your bike which would allow the voltage to rise above 12-14V at 4000rpm and up?
Or, is there an intermittent open circuit in your earthing for the instruments which is caused by engine vibration above 4000rpm?

Hope this helps.

[kz]

Hi Brit 7.11,

Thanks for your inputs.

1.
My bike is running very good, no misfiring etc.

Do you think there still can be any disturbance from the coil?

It is possible to disconnect the lead at the tacho and replace it with a separate new lead, connected directly to the other coil.

It is worth trying....

2.
I even thought of mounting an oscilloscope on the bike, but gave up that idea, however I think I will try to connect a multimeter for monitoring the tacho 12 V mains (I changed the regulator half a year ago and measured the voltage accordingly).

Also worth trying...

3.

Do you think that the bike will run correctly if I have a malfunction at the ignition trigger?

[Anonymous]

Well, I think that the tacho is more sensitive to small changes in its signal. I suppose that the bike could run ok with an ignition system fault (coil or ignitor) which would cause a tacho problem.
When I changed the coils on my bike to Dyna's, it ran much cleaner. I wouldn't have said there was anything wrong before. Also, if you read the ads for "Splitfire" spark plugs they state that engines misfire many times a second. As the bike gets older this would probably get worse.
I just get a gut feeling that engine vibration above a certain rpm is causing an intermittent open circuit somewhere, possibly even in the Tacho itself.

Don't give up!!!

[kz]

1.
I mounted a multimeter on the bike and connected it almost directly to the tacho mains.

Without headlight on steady 14,4 V and with headlight on 12,7V throughout the rpm-range.

The tacho behaives the same way with or without headlight on/off.
2.
I connected a complete new wire from the tacho directly to the other coil.

No difference in tacho behaivior.


3.
I think that then I run the tacho in the bench I have a nice square signal with constant voltage and then it is in the bike the signal is not so nice.

Something in the tacho must be able to take care of the ripple in the signal??

I tried to see if there is any crack on the tacho board, but could not found any.

I almost got it perfect by changing the capacitors the first time so I think I will try to change them again.

Any suggestions are very welcome

[Anonymous]

noise on the line

Sounds like the tacho is being messed up by noise on the tach signal line. The signal from the signal generator will be specifically just that, no 2nd harmonics or anything, they take huge care when theyre building them to make sure of that.
On the bike its a different thing, theres huge amounts of electrical noise flying round, and bare unshielded wires to the tach in the loom acting as a big antenna. Sounds like your picking up a spurious noise signal and its bouncing the tach all over the place.
What you might look for is a spurious signal that is higher and causing the reading to spike up every so often. If you find the culprit (and the scope is ideal for this) its not a huge job to make up a noise filter to just block that frequency range. Theres a lot of this going on in homebrew efi systems being triggered by noise and causing odd running etc.
You may even be able to trace whats putting out the spurious noises and get early warning of something failing..
A filter will usually consist of a tuned circuit, either to remove a certain set of frequencies , or to only allow a certain set to pass (bandpass filter), maybe the capacitor you are changing is part of such a circuit and is tuning the noise out, maybe a inductor has shorted a turn or two out of its coil somewhere else and has changed value...
Happy hunting!

[kz]

IT WORKS AND HAS DONE SO FOR 3 OURS!!!!!

So, I was suspicius about the capacitors so I also changed the two Tanthal-capacitors on the circuit board without succsess.

After reading MrFluffys post about filtering I came back to the electrolyt capacitors and my first partly succses changing them.

As I wrote before I was an unlucky owner of two tachos, both bouncing.

So I started with the next tacho and changed the two eletrolytic capacitors and mounted it back and IT JUST OPERATED AS IT SHOULD .

I think that either I messed up the first tacho by soldering the wrong capacitor I got from Elfa at the first time or there are really different errors on them??

Now then I have a tacho mounted that works I'll think I give this matter a rest for a the next future.

However, on the tacho board is really not much mounted and there can only be a couple of recistors, two eletrolyt capacitors, two thantal capasitors, one diod and a special IC marked ND SM014.

I could not found the special IC anythere and it probably contains some OP-Amplifiers, it could be that this IC was distroyed on my first tacho.

Anybody who knows there to get this IC or an eqvivalent?

I want to thank you all, especial Brit 7.11 and MrFluffy for your inputs and chearing me up (was a little bit *@%^$*@%^$*@%^$*@%^$ed of tachometers for a time).

It would also be very interessting to here if JD has come up whith something regarding his tacho (after all he started all this).

[Anonymous]

Good stuff!!

[kz]

JD,

The tacho with the replaced capacitors still works like a dream!!!

Have drove 1500 km now.