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308 Speedo Repair/Rebuild

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

  1. AN-M

    AN-M Formula Junior

    Jun 30, 2012
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    Norway
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    André
  2. alhbln

    alhbln Formula 3
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    Mar 4, 2008
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    Adrian
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  3. Robz328

    Robz328 F1 Veteran
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    Mar 16, 2009
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    Rob Hemphill
    (this isn't a fix for a sender problem; you will likely need to replace it and possibly some wiring; calibration of the new board is "on the bench" and real results would disagree with expected results if there is a defective sender circuit. Also, US "miles" versions will have the km inner labeling which is only an indication of the mathematical conversion on the faceplate...no circuit here for "km" for the "miles" version; an actual "km" European version requires the "x" version circuit board to be ordered; for those who "convert from miles to km" by ordering a "km" faceplate and using the "x" board, for accurate ODO reading, you would need to "roll it up" to read ODO km...a higher # [is this possible, and legal? just sayin'])



    Excellent work, Adrian!

    I reviewed the link and it is well-done...a simple install for any of us. Time for the 308 owners to upgrade!

    I still recommend a sticky in the "Electrical" section.
     
  4. BigTex

    BigTex Seven Time F1 World Champ
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    Dec 6, 2002
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    Bubba
    There's a dual range unit just posted in FerrariAds, but it's also on eBay.

    Talk to the seller if you need one he'll cancel eBay auction.
     
  5. ChallieMoto

    ChallieMoto Rookie

    Jan 22, 2013
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    Matthew
    Thanks to BigTex for guiding me over to this thread! I do currently have a dual range that should fix that problem that I would gladly cancel on eBay and sell to a fellow forum member! Just pm me or drop a message on my classified ad!
     
  6. BigTex

    BigTex Seven Time F1 World Champ
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    Dec 6, 2002
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    I should buy it but I don't get paid until the 18th, maybe 19th...
     
  7. ChallieMoto

    ChallieMoto Rookie

    Jan 22, 2013
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    BigTex if it doesn't sell before your payday, I would gladly hold it for you.
     
  8. BigTex

    BigTex Seven Time F1 World Champ
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    Well, as you see in this thread here, it's so frustrating, the OEM obsolete microchip.....some of our more talented owners have re-engineered the whole thing!!

    I appreciate it..."any spare part you have in the garage will never be needed".
    One of my axioms.....
     
  9. BigTex

    BigTex Seven Time F1 World Champ
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    Dec 6, 2002
    70,742
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    Bubba
    The eBay auction window should be long enough.

    Any other chatter that wants it will save me $300.

    Why does it show some mileage?
     
  10. ChallieMoto

    ChallieMoto Rookie

    Jan 22, 2013
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    Matthew
    I wanted to double check all the gearing and mechanical functions to make sure it was working properly before selling it! I had it in storage for sometime before this.
     
  11. ZOOOOMZ

    ZOOOOMZ Karting

    Aug 14, 2013
    231
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    Tim Cronin
    I'm an envious 328 owner, whose speedo is currently intermittent. What's the outlook for a gorgeous board like this for 1988 328 owners?
     
  12. Ferraridoc

    Ferraridoc F1 Veteran
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    Jun 20, 2012
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    Patrick
    It's your sender
     
  13. alhbln

    alhbln Formula 3
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    Mar 4, 2008
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    Adrian
    I have started on a "Type 2" board for the newer Speedos but this will take a bit. Should not be a problem to do one though.
     
  14. ZOOOOMZ

    ZOOOOMZ Karting

    Aug 14, 2013
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    Tim Cronin
    Ferraridoc,
    Thanks for the reply, but unfortunately, it's not my sender. I, too, started there, but I've replaced that, and still have the problem. I've also been through the wiring, connectors, and even replacing all of the electrolytic capacitors on the Speedo circuit board, but the problem persists. I have the symptom that when it fails, it momentarily pegs full scale, then drops dead.... happens when moving or when sitting still, by the way. Sometimes, it pegs full scale momentarily, then returns to normally functioning.... Always, I can smack the instrument pod and bring it back, hinting that maybe a dirty/loose connection might be the culprit, but I've cleaned/scrubbed everything, including resoldering the PCB connections (in case a cold solder joint might be the cause), to no avail. Also, I cannot cause the failure by smacking the instrument pod... At this point, I'm left with sending to Palo Alto Speedo or replacement. Hence, my question about this cool update. If I'm going to spend the $$$ for repair or replacement, better to modernize at the same time!
     
  15. alhbln

    alhbln Formula 3
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    Adrian
    If your ODO still works, then it's likely a failure of the BC237B and BD370C transistor pair on your type 2 circuit board. The BC237 NPN drives the base of the BD370 PNP, which switches plus to the needle's coil driver.
    Try to replace both, this might already fix the issue. (If you can't source a BD370C, try a BD140, the case is a bit larger and base/collector pins are swapped, but the specs are similar).
     
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  16. ZOOOOMZ

    ZOOOOMZ Karting

    Aug 14, 2013
    231
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    Tim Cronin
    Thanks for the suggestion, Adrian. Unfortunately, the ODO and SPEEDO function or fail together, while the TACH is unaffected, and functions properly regardless of SPEEDO intermittence. Could this transistor pair still be the culprits, or do you have any suggestions for the root cause in this case?
     
  17. alhbln

    alhbln Formula 3
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    If both Speedo and ODO just stop working then i would suspect either the sensor (which has been replaced already) or the connector from the sensor to the car wiring is bad. That the needle pegs full scale and the ODO is failing is an indicator that the RCA 349 chip on the circuit board has gone bad, unfortunately. I'm not aware of a NOS source for RCA 349 chips.
    Maybe you could borrow a functional Speedo for testing to make sure it's not the car wiring/sensor? I'm pretty sure that it's the RCA chip but that would be a good test to do anyway.

    The Tach is driven by the ignition, it would not be influenced by a Speedo/sensor defect.
     
  18. Ferraridoc

    Ferraridoc F1 Veteran
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    Jun 20, 2012
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    Ahh, well that sounds a bit more complicated. In my game, all abdominal pain is appendicitis until proven otherwise, therefore all speedo problems are the sender until proven otherwise (common things occur commonly). I too checked all the connections (didn't crack open the speedo, but did the dash light upgrade) and the problem persisted, but mine was just failure to work, then suddenly working after 25 mins of driving, so most likely a temperamental semiconductor/capacitor in the sender getting a bit of thermal excitation. I've put another one (second hand) in, but haven't tested it yet.
     
  19. Dino Milano

    Dino Milano Rookie

    Oct 30, 2008
    49
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    Dino M.
    Hi Adrian,

    Very nice work you did!!

    Do you think the board 'll work for a Dino 208 GT4?

    All instruments are the same but?

    Best regards

    Dino
     
  20. glenv6

    glenv6 Formula 3

    Jul 4, 2011
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    Glen
    That is good news! Thank you for your efforts.
     
  21. alhbln

    alhbln Formula 3
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    Mar 4, 2008
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    Adrian
    Yes, the 208 and 308 instrument electronics are identical, sorry that i did not mention this in the list!
     
  22. ZOOOOMZ

    ZOOOOMZ Karting

    Aug 14, 2013
    231
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    Tim Cronin
    In fact, I'm happy to be a Beta tester, if you need one. Along with all the other Type 2 owners, I thank you for this terrific project. I'm sure, no matter how I resolve my current issue, it will fail again sometime in the not too distant future, and your project will be the solution. Thanks, again!
     
  23. alhbln

    alhbln Formula 3
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    #123 alhbln, Jul 21, 2014
    Last edited by a moderator: Sep 7, 2017
    Thanks for the offer, will get in touch as soon as i have some beta boards (First need to do a bit of research and design, and sell the Type 1 boards to get some budget in for the Type 2 board production).

    I've added an image with the two original circuit board versions for easier identification below.
    Image Unavailable, Please Login
     
  24. ZOOOOMZ

    ZOOOOMZ Karting

    Aug 14, 2013
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    #124 ZOOOOMZ, Jul 22, 2014
    Last edited by a moderator: Sep 7, 2017
    Thanks for the further info, Adrian. I would only comment that my 1988 328 speedo (which uses a bottom-mounted gearbox sensor) has a Circuit board that looks different from your Type 2 Circuit board. Perhaps this is a Type 3? There are at least component value and board shape/layout differences, and the chip is an RCA 806, rather than the RCA 349. Don't know if that's material to your plans... Here's a snapshot of the board in my speedo:
    Image Unavailable, Please Login
     
  25. ZOOOOMZ

    ZOOOOMZ Karting

    Aug 14, 2013
    231
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    Tim Cronin
    Sorry, one other observation: the RCA 349 or RCA 806 - maybe they're date codes (1983, 49th week, 1988, 6th week)? I notice now that the 92967 appears on both ICs.
     

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