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308 Speedo Repair/Rebuild

Discussion in '308/328' started by alhbln, Aug 22, 2013.

  1. alhbln

    alhbln Formula 3
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    Very interesting, thank you! It looks like a revised Type II Board, one resistor and one capacitor less than the Type II and now it's a two layer board. Since the board shape is different, let's call it Type III as you suggested. The wire colors are identical to the Type II, the white connector is most probably the supply for the Speedo.

    I had different 929 markings on two Type II boards so was assuming that this would be the date code and the three digit code the type, but it might be the other way round. Need to see more samples to but some meaning into this. Unfortunately there is virtually no documentation about RCA chips which were designs for OEMs such as Marelli.

    Could you also post a photo of the bottom side please?

    Very helpful, thank you,
    Adrian
     
  2. ZOOOOMZ

    ZOOOOMZ Karting

    Aug 14, 2013
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    I will gladly post a photo of the bottom side, but I'll have to photograph it, first. I may be able to tear it down and snap a pic this weekend. Please bear with me, and I'll post it as soon as I can. (can't believe I didn't photograph the bottom side too...)

    As far as 'type' designations, even if you can design a universal one that is shaped and functions such that it will replace either the Type 2 or the Type III, I agree that for now, it may be best to refer to these original boards as unique. I wonder when the change happened, from Type 2 to Type III???
    Many thanks,
    Tim
     
  3. alhbln

    alhbln Formula 3
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    #128 alhbln, Jul 22, 2014
    Last edited by a moderator: Sep 7, 2017
    Veglia did board revisions from time to time to fix errors or reduce components to keep the cost down. There is also a second revised version of the Type I board, see below.

    I'll just create another board (Type III) with the circuit design i do for the Type II board since the ODO stepper and Speedo drive are similar. The Type I board uses different hardware, so i need to do a new hardware design for Type II and III.

    Not sure yet when the change from Type II to Type III happened, i would guess somewhere between '84 and '88.
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  4. gerritv

    gerritv Formula 3

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    I think you will find that the Type II/III boards do not drive a stepper motor but provide a pwm or dc drive to a dc motor for the odometer.

    Gerrit
     
  5. gerritv

    gerritv Formula 3

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    Zoooomz, did you get my earlier email?

    Gerrit
     
  6. alhbln

    alhbln Formula 3
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    Yes, correct, that will be the area i need to change in the next circuit design. Looks like it will be a bit simpler to design since i can do that task mostly in software :)

    The only thing which is a bit puzzling right now is that the newer boards do not have a trimmer for the Speedo calibration anymore, looks like this has been handled in the initial mechanical setup by the factory.

    Thanks,
    Adrian
     
  7. gerritv

    gerritv Formula 3

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    There are other differences as well. The Type II/III speedos have a very different meter movement, with 3 wires. It doesn't even look like a meter movement. This might explain the missing calibration trimmer etc.

    I will email you some photos, I am over my limit.

    Gerrit
     
  8. Crowndog

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    #133 Crowndog, Jul 23, 2014
    Last edited: Jul 23, 2014
    Well now, since I have a '85 QV with a type II or III board I guess I won't be needing the two SAY chips I have been hoarding. Any offers? Anyone? They are unused NOS in static free holders.
     
  9. alhbln

    alhbln Formula 3
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    #134 alhbln, Jul 24, 2014
    Last edited by a moderator: Sep 7, 2017
    In the Type 2 Speedo the ODO has a three wire connection, GND, VCC and pulse. The pulse width is not fixed, as the width is synced to a number of incoming pulses. Each pulse triggers a single ODO movement. (I would guess that there is a load switching circuit in the ODO which is triggered by the RCA's pulse out, to take the load off the RCA chip. That would explain the VCC supply to the ODO.) Around 128 ODO pulses move the day counter by one kilometer (similar to the Type 1 Speedo).

    The Speedo has two wires, GND and pulse. The pulse width is also not fixed, which is different to a classic moving coil mechanism as in the Type 1 Speedo.

    Thanks for the offer sending photos, much appreciated!

    Cheers,
    Adrian
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  10. alhbln

    alhbln Formula 3
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    You're right, 92967 is the RCA OEM type code and the three digit number most likely the date code. Year and week coding make sense as you posted above.

    Thanks,
    Adrian
     
  11. gerritv

    gerritv Formula 3

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    Looking at my spare speedometer, I think the 3 wires are actually the speedometer needle drive. The needle is mounted to a round cup that rotates around a disc that spins. The 3 wires seem to go to a coil, I suspect that actuates a magnetic field dragging the cup/needle with it. The 2 wires go to the drive motor. I will in the next day or so setup a bench test and disconnect wires in turn to verify this behaviour.
    The unit I suppose exhibits linear & predictable behaviour, hence no tirmmers etc.

    Gerrit
     
  12. alhbln

    alhbln Formula 3
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    You're right, i mixed up the Speedo and ODO wiring, assuming that the bottom device is the ODO drive. Will correct that in the next diagram update.
     
  13. AN-M

    AN-M Formula Junior

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    Wouldn't you know it!? I got something, from one of my favorite countries, in the mail today! And best of all, customs didn't bother charging me VAT. I love freshly populated PCBs! Thanks Adrian and give me a poke if you have other interesting projects ahead!
     
  14. alhbln

    alhbln Formula 3
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  15. alhbln

    alhbln Formula 3
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    #140 alhbln, Jul 29, 2014
    Last edited by a moderator: Sep 7, 2017
    Below is a type 2 Speedo owned by our forum member ME308. This is one quite interesting as it is a transitional model, probably made around autumn or winter '80. The internals are a type 1 Speedo with an additional small Veglia circuit board mounted on top of the standard type 1 board to make it compatible with the later type 2 sensor signal.

    From the outside it looks just like a type 2 Speedo, but the ODO moves forward in 12 steps for one km/h instead of having the smooth movement of the ODO in a type 2 Speedo.
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  16. ME308

    ME308 Formula 3

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    Adrian, you are certainly the world`s most knowledgeable source as for 70 and 80ies Ferrari speedometers and digi-/dinoplexes ... and who knows what else ;)
     
  17. gerritv

    gerritv Formula 3

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  18. ZOOOOMZ

    ZOOOOMZ Karting

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    Adrian, Just want to let you know, I haven't forgotten that I owe you pics/measurements of my existing Type III board. I finally got to remove the speedo assembly this past weekend, and hope tonight to be able to disassemble and document for you. Please bear with me; seems other things in life take priority over my prancing horse. Imagine that!

    Thanks,

    Tim
     
  19. G. Pepper

    G. Pepper F1 World Champ
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    Yeah, I spent the first few days of ownership trying to figure out the speedo. It starts on 10 and is +10 all the way to 90, so at least it's consistent.

    I have a to-do list. This is not at or near the top. ;)

    Dead parking brake and exhaust whistle are the first two things (The brake handle is actually bent toward the driver, so I'm guessing fun has been had with the car. :D ).

    Cheers,

    George
     
  20. alhbln

    alhbln Formula 3
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    Great, thank you very much!
     
  21. ZOOOOMZ

    ZOOOOMZ Karting

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    #146 ZOOOOMZ, Aug 6, 2014
    Last edited by a moderator: Sep 7, 2017
    Here are photos and a sketch documenting the Speedo board in my 1988 328GTS. I believe they are mostly self-explanatory, but here are a couple of comments:

    Apologies for the English scale in the pictures, but metric dimensions on the vernier.

    Photo #6 the plastic mounting boss, showing the screw hole and the index boss
    Photo #7 is the connector header (beside the IC) This, and photo #1, also shows the mounting screw with fiber washer, and the indexing boss (through the hole at the end of the 220uf capacitor)
    Photo #8 is the other PCB and its connector (on the meter movement)

    The .pdf is a dimensioned sketch of the PCB showing hole locations and diameters

    Please let me know if you need any clarifications or further information.

    Huge thanks for taking on this project!
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  22. alhbln

    alhbln Formula 3
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    Very cool, thanks a lot! The circuit looks similar in approach to the type 2 pcb and the odo/speedo also looks like the type 2, so a single new circuit design should cater for both speedo types. I need to do two different pcb shapes though as the sizes/screw hole positions seem to be different.

    Cheers,
    Adrian
     
  23. ME308

    ME308 Formula 3

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    #148 ME308, Aug 24, 2014
    Last edited: Aug 24, 2014


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    this rare find 280km/h speedo circuit board came from a EURO 308 2Vi

    actually my plan was to exchange this speedo with the one in my US 308 2Vi to get rid of the odd 85mph max speedo

    he, he,... easier said than done, like always ;)


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    after installing the 280km/h speedo, all three - pointer, odo and day counter - only displayed exactly half of the speed driven and distance travelled

    fortunately enough, crowd sourcing on this board and Adrian`s excellent work found out that the top mounted US type 1 sensor only sends out 4 pulses to the US 85mph speedo - my new EURO 280km/h speedo needed 8 pulses of course since it "expected" the type 2 bottom mounted sensor for the EURO cars (which indeed sends out 8 pulses)


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    fast forward to the installation of Adrians`s great new type 1 circuit board -
    it is converting mph into km/h perfectly and also takes care of the 4 to 8 puls transformation


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    from personal experience I can highly recommend this speedo circuit board !
    it has been working perfectly from day one - pointer, odo and day counter are incredibly accurate now !

    once again thank you Adrian, I could not be happier :)

    .
     
  24. ZOOOOMZ

    ZOOOOMZ Karting

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    Greetings, Adrian... Have you had any chance yet to pursue the new design for a Type III board for the 328? I'm using a spare speedo now, until I can get my original one fixed, but still want to get back to my original after I can get it fixed (with your new board!)... BTW, I'll want to roll my original odometer forward, to account for the miles I've put on my car with the interim speedo in place. Will your board support rolling the odometer forward to make it show correct mileage?
    Also, I'm thinking of changing to different size tires, which will have slightly different circumference from OEM tires; will I be able to calibrate the new speedo board to show accurate readings?
    Thanks again, for taking on this project; we 328 owners appreciate your efforts in advance!
    -Tim
     
  25. alhbln

    alhbln Formula 3
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    Tim,
    i've started on the Type 2 and 3 redesign, but it will take some more weeks, please be patient :)

    You can easily roll forward your speedometer manually, all it takes is to remove the dial face and unlock the small clasp on the left side to remove the dials and readjust the numbers.

    I should be able to adopt custom tire sizes by changing a parameter in the board software. Just tell me the tire rolling distance when you order a board, and if you have a km/h or mp/h tacho.

    Best,
    Adrian
     

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