I want you to see how the PCB of a diesel Felicia with tachometer looks like. I marked with a dotted rectangle the area where the IC for the conversion of TIS resides.

 

 

And here is the PCB from a 1.3 SPI with tachometer looks like. Again I marked with a dotted rectangle the area where the extra IC should be mounted to resemble with the diesel board and have full tachometer functionality.

 

Edited 27 June, 20169 yr by RicardoM

Please advise on conversion and im interested in your explanation why a zener diode is partially correct but will not work

Please give me an idea what level of details should I go into on explaining the Zener solution. How skilled are you in electronics? I don't want to bore you with basic things if you're advanced.

@ Ricardo. Very nice writing. Thank you. I opened my 3 spare tacho's and I found a few differences. First of all is that 2 of them are from carburetor model and the one is from an Mpi model. Probably that is the one I have to work with. So... My next step is to source an HCF4040B IC?

 

Thank you

Since you didn't mention what level of detail should I go into, I will keep it simple.

 

I will start by explaining why using a Zener diode wouldn't work. I've used an electronics simulation program (Proteus 8) to see how the schematic below works.

 

 

I've simulated the signal coming from the alternator using a sinusoidal signal generator 12V peak to peak. There is our 5V1 Zener diode, the 4040 IC and an oscilloscope to visualize the signals. Here is what we get.

 

 

On channel 1 (yellow trace) we have our alternator signal.

On channel 3 (magenta trace) we have the signal after the Zener diode.

On channel 2 (blue trace) we have the output from HCF4040B.

 

As you can see the shape of the magenta signal is totally unacceptable, meaning it is not a square wave. The IC that actually drives the tachometer gauge (KEFB-842) is right after HCF4040B and needs a square wave input signal.

First of all is that 2 of them are from carburetor model and the one is from an Mpi model.

Interesting... Where did you get 2 Felicia instrument clusters with tachometer for 1.3 carburettor engines? I thought there aren't any on the UK roads.

 

Probably that is the one I have to work with. So... My next step is to source an HCF4040B IC?

The easiest would be to send me by e-mail high resolution photos of the PCB from MPI model. I will annotate them in detail and reply in here. There are 13 type of PCBs and I have to be accurate. I will explain exactly what to buy too.

 

First of all is that 2 of them are from carburetor model and the one is from an Mpi model.

Interesting... Where did you get 2 Felicia instrument clusters with tachometer for 1.3 carburettor engines? I thought there aren't any on the UK roads.

 

Probably that is the one I have to work with. So... My next step is to source an HCF4040B IC?

The easiest would be to send me by e-mail high resolution photos of the PCB from MPI model. I will annotate them in detail and reply in here. There are 13 type of PCBs and I have to be accurate. I will explain exactly what to buy too.

 

I lived in Greece and the last year moved to London, back there, there are quite a lot carburetor models.

I understand the basics about signal imputs, 5V,12V square e.t.c. so they are strange to me.

As soon as I get the cluster to my hands and open it I will send you the photos.

Edited 1 July, 20169 yr by ThomasItis

I lived in Greece and the last year moved to London, back there, there are quite a lot carburetor models.

It's good to know about the existence of carburettor Felicias in Greece.

Is there a Greek forum dedicated to Felicia?

It's good to know about the existence of carburettor Felicias in Greece.

Is there a Greek forum dedicated to Felicia?

No unfortunately there aren't left to many Felicia's in Greece, especially carburetor models.Maybe MPi's and that's it. I own my Felicia since 1997, when my father sold the Favorit and bought the Fely. On my 18th birthday the Fely came to my hands and since then despite the fact that me and my father have bought,sold and changed a lot of Skoda's the Felicia is still there under my supervision and ownership. 

RicardoM i carefully drilled and soldered the additional component and still get the initial movement at startup on the rev counter is there something i have missed as im thinking i need to remove the original sinusoidal signal to allow the new square wave or as i see from your explanation diagram can i just simply splice yellow green input signal wire and solder the HCF4040B pin 10 and 9 as shown or is this too simple my knowledge of electronics are basic but i am an experienced mechanical engineer, i have enjoyed this little project and hope it has aided other members of the group, no harm done if it doesnt work maybe i should look out for a diesel instrument cluster with fitted tacho

Substan

One obvious question is this: did you see with your own eyes the donor instrument cluster working 100% on donor car? Tachometer included.

 im thinking i need to remove the original sinusoidal signal to allow the new square wave

I don't understand what you mean.

As I've told to Thomasitis too, take a photo of the PCB to see exactly what you did and I will advise in detail.

Edited 6 July, 20169 yr by RicardoM

Must admit i never saw donor tacho working but is does seem strange that fitting extra component without severing original signal link would give the required waveform putting this in basic terms if water flows through a pipe at constant velocity and i introduced another pipe with variable velocity unless i stemmed the flow of constant velocity i wouldn't see the variable flow at the end of the pipe

Must admit i never saw donor tacho working

That is not good news.

 

...but is does seem strange that fitting extra component without severing original signal link would give the required waveform putting this in basic terms if water flows through a pipe at constant velocity and i introduced another pipe with variable velocity unless i stemmed the flow of constant velocity i wouldn't see the variable flow at the end of the pipe

I've read your comparison several times and I can't follow your logic. Is anyone else understand what he means?

 

Anyways, let's try one last solution. See photo below. I zoomed in the area where the tacho posts and tacho IC are. During operation the vibrations of the car are transmitted to the instrument cluster too. The components with larger mass have bigger inertia and exert bigger stress on PCB and solder joints. In time the copper tracks crack. In our case the most sensitive areas are around those 3 posts where the tacho is fitted. I recommend soldering thin insulated wires (shown in magenta) to replace existing copper tracks.

 

 

In case you need evidence that such method worked for others, here is a photo of a PCB from a Felicia 1.3 SPI. I bought this instrument cluster being 100% functional but as you can see somebody 'repaired' it previously. I'm not saying the repair didn't work but I hope you'll do a much cleaner job.

 

I also recommend reading this article about common soldering problems. You will learn how to recognize pads or tracks that need resoldering. A good magnifying glass and plenty of light are a must.

RicardoM thanks again for your help when i can i will try again at the conversion and check all contacts areas mentioned, i have reviewed all the history of this project and i have a question perhaps no relationship to tacho but what is the purpose of the door contact as a signal input for the ECU?

Depending of coolant temperature a preheating phase is activated by the driver's door switch. In other words, after the driver opens and closes his door a preheating cycle occurs. That speeds up the process of starting up the engine and taking off.

Edited 10 July, 20169 yr by RicardoM

👍👍❤️

Hello all , would a dashboard with part number

443431143820 443431096820

OEM6U0919033C be a good donor board to replace the clock'd on my felicia 1.9d ? Thank you

20 hours ago, FernandoPessoa said:

 

OEM6U0919033C be a good donor board to replace the clock'd on my felicia 1.9d ? Thank you

 

2 examples to look, they fit to your 1.9

 

https://izap24.ru/tovar/18888819_schitok-priborov-pribornaya-panel-skoda-felicia-1999-6u0919033c.html

 

https://www.ekodily.cz/e-shop/1385584-cz-skoda-felicia-19d-64-hp-manual-47-kw-1896-cm3-5--pristrojova-deska-6u0919033c-pristrojove-desky-displeje/

Skoda Felicia 1.9d 64 hp manual 47 kW

 

but searcing for: 6U0919033C

you can find almost everywhere (ebay etc).

This is from Spain

https://izap24.ru/tovar/18888819_schitok-priborov-pribornaya-panel-skoda-felicia-1999-6u0919033c.html

extremely close to you.

 

 

Thanks for your help D.FYLAKTOS. Although the last link is the same as the first u sent ive found several in Spain and even here in Portugal. On another note about the speedometer drive u helped me with several links is still a no go. I ordered it from Singapore but got the order cancelled cause afterall they had no stock on it. Russian sites dont even respond to my emails.

 

Thanks again \m/

15 hours ago, FernandoPessoa said:

Russian sites dont even respond to my emails

 

I had the same problem in the past, some Russian e-stores don't have paypal or credit card or Western Union payment method and when you order from Europe you have to pay them via Bank transfer in a specific bank (which of course does not have a branch in Greece) or with sites like Yandex or similar which have no english section etc.

It's a nightmare.

A followup to my quest to get that speedometer gear : autoland site in Kazakhstan has the part i need for around 5 euros. I would have to contact dhl to get an estimate on the sending cost. I was given a cost of 190 euros for it. And they only replied when i translated to Russian. The search goes on 

Edited 3 March, 20233 yr by FernandoPessoa

On 03/03/2023 at 21:42, FernandoPessoa said:

I was given a cost of 190 euros for it.

 

😲

 

 

Is there a way to fit cluster with tachometer from carb 1.3 to 1.6 mpi. I tried and everything works except tachometer.