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Specs on SAY115Y IC for speedometer?

Discussion in 'Technical Q&A' started by gerritv, Jul 3, 2004.

  1. gerritv

    gerritv Formula 3

    Jun 18, 2001
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    Hi
    The 308GT4 speedo has an obsolete IC at its heart. Does anyone have a source for old ITT parts books? I am looking to substitute or replace the pc board with something equivalent that works for longer than a year :) Searching Google has not resulted in success except to find a source that might have some in stock.

    Any hints appreciated.
     
  2. gerritv

    gerritv Formula 3

    Jun 18, 2001
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    Hi
    Just bumping to top, hope everyone had a great weekend.

    If anyone can point me to a source of the spec sheet for a SAY115Y, it would be greatly appreciated. Else I will have to start from zero to build a replacement board for the speedo.
     
  3. KurtK328

    KurtK328 Formula Junior

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  4. gerritv

    gerritv Formula 3

    Jun 18, 2001
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    Hi Kurt,
    thanks. I knew about that site. What I was looking for was the specs so I can replace it with something that is not close to unobtanium :) But I might end up just trying to get the original chip.

    Gerrit
     
  5. KurtK328

    KurtK328 Formula Junior

    Mar 6, 2001
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    Who made the chip?
     
  6. gerritv

    gerritv Formula 3

    Jun 18, 2001
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    Hi
    It was ITT Germany. Date code is 8244. ITT (now Intermetall) sent me a copy of the datasheet from 1976 so I now have what I need.

    Now to design a replacement board!
     
  7. KurtK328

    KurtK328 Formula Junior

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    Excellent - keep us posted.
     
  8. DGS

    DGS Three Time F1 World Champ
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    May 27, 2003
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    Anyone know how many pulses per mile (or per Km) the sender transmits? (I think the RPM sensor on a 328 puts out 144 pulses per rev, but I don't have any data on the speedo sender.)

    Given the pulse-per-km figure, it's then just a matter of programming the appropriate generic code slice module. Easy ;)

    (Real programmers don't write comments ... the code is obvious.) ;)
     
  9. gerritv

    gerritv Formula 3

    Jun 18, 2001
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    Hi DGS
    Not quite that simple of course. The meter requires a specific current per KM/h and the odomoter is driven by a (sort of) stepper motor. Looking at component counts to use a PIC vs. Frequency->Voltage converter and rate multiplier, the non-PIC solution wins.
    Converting this to a digital speedometer would of course benefit greatly from using a PIC.

    Gerrit
     
  10. gerritv

    gerritv Formula 3

    Jun 18, 2001
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    Hi
    I took a good look at the sender on my GT4. Part is 68 1041-6K, 4 imp/g, aka 4 impulses per revolution. The next question to answer is how rev's per mile or KM.

    Gerrit
     
  11. DGS

    DGS Three Time F1 World Champ
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    I don't have books on a GT4, but on the 328, the pulse generator reads off a gear driven by the gearbox oil pump shaft on the transfer case. It's hard to tell from the exploded view what drives the oil pump, so I can't really tell what the ratio is between the oil pump shaft and the half shafts.

    The rotation per mile of the half shafts can be read from your tire specs (or computed from overall wheel diameter). AVS Sports in 225/50-16 would be 836 rev/mile on a 16x7 rim, according to Yokohama's data. (823 on Pilot Alpins, 829 for AVS es100.)

    I was, of course, kidding about the "simple" part. ;) It sounds like you're on the right track as you're trying to repair, not replace. But I was a little surprised, when I looked into it a while back, how cheap the generic instrumentation processors have become (complete with on-chip timers, A/D converters and D/A converters). The development/test/emulator rigs for them are another matter, of course, but most accomodate a standard serial programming interface and the Gnu C++ complier has cross-compile options for most of them. (I was looking into using an 8051-series to replace the guts of the Marelli multiplex. Surprisingly, the 8051 doesn't have the address space for the Marelli's overly-complex map. But an M32R would do the job (and have loads of spare proc cycles left over).)
     
  12. Nickt

    Nickt Formula 3

    Feb 24, 2006
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    Bump
    I would be very grateful if this post could be updated. My 308's speedo works but the odometer has stopped going round. Could that be the SAY115Y? or when it fails does the whole speedo fail?
    This is my car's 3rd speedo a far as i am aware.
    If it is the stepper motor is there an alternative i could use?
    Regards
    Nick
     
  13. alhbln

    alhbln Formula 3
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    Could be either the SAY115Y output pins for the odometer (pin 3 and 5) or (if you are lucky) just the BC327 transistor behind the SAY115Y, driving the odometer coil.

    You might want to try exchanging the transistor first as this is the cheapest option. On and Multicomp are still supplying this type.

    As long as sensor inputs are coming in, you should see alternating high and low states on pin 3 and 5. If the pins 3 and 5 don't change their state but the speedo works, then unfortunately the SAY115Y is broken. If both the odometer and speedo won't work, then chances are that the sensor itself is broken.
     
  14. Nickt

    Nickt Formula 3

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    Thank you!
    The speedo definately works, but the mileage counter doesnt. Can I test this out of the car using an multimeter?
     
  15. alhbln

    alhbln Formula 3
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    #15 alhbln, May 24, 2013
    Last edited by a moderator: Sep 7, 2017
    You would also need to remove the sensor to create an input signal to test with. With an input signal there should be an alternating state on the two pins marked with the yellow arrows. The third yellow arrow marks the transistor which would show the same effect (speedo works but not odo) if it's broken.
    Image Unavailable, Please Login
     
  16. Nickt

    Nickt Formula 3

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    If I were to buy a cheap signal generator, could I use that to simulate the sensor?
     
  17. alhbln

    alhbln Formula 3
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    The SAY115Y input triggers on ground, so a cheap square or sine wave generator which supplies a 0-5V output signal should work.
     
  18. Crowndog

    Crowndog F1 Veteran
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    I may be wrong but everything you want to know and some of what you don't want to know has all been covered here in the 308 section. Please check with the search function and you will find alternatives, specs, chip variations, failed group buys (yours truly) etc. Simply search on say115y
     
  19. Paul_308

    Paul_308 Formula 3

    Mar 12, 2004
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  20. Nickt

    Nickt Formula 3

    Feb 24, 2006
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    Hi Guys
    My speedo's odometer packed up, so I bought a replacement chip from Ireland fitted it and went out for a drive. For the first time in ages I had an odometer... for exactly 1.6 miles, then it stopped again. In the next 20 miles it only moved .4 mile. The speedo is perfect and much more accurate then it ever was.
    I have a new speedo sender so I know its not that.

    Any ideas? I contacted Dönberg thinking that the IC was faulty and this was their reply:

    Dear Nick

    Sorry you are having trouble

    This is the answer back from the supplier


    Hello Maura,

    we have sold 117pcs of SAY115Y in total
    There were 25 orders to 18 different customers.
    Among them were 3 orders from you with 11 pcs in total.

    So far we never received a complaint.

    They passed our visual authenticity inspection based on the US standard IDEA-STD-1010-A
    We check every incomming AND outgoing batch according this standard.
    Furthermore we stored and shipped them ESD safe in highshieled bags.

    Unfortunately we don't have any of them in stock anymore and we don't see any trustworthy sources out there.


    So I guess I am up a certain creek.. Does anyone have a chip they will part with? and working speedo, a working pcb? I live in London, England.
     
  21. alhbln

    alhbln Formula 3
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    Not sure if this is of help but i've received two more Speedometers for repair, so will design a new replacement PCB based on standard components. Parts cost for full PCB should be considerably below a single SAY chip. If you want to become a tester, let me know :)
     
  22. Nickt

    Nickt Formula 3

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    YES PLEASE!!!!!!!!!!!!
    YES PLEASE!!!!!!!!!!!!
    YES PLEASE!!!!!!!!!!!!

    Sorry, yes please I would like to become a tester. do you have any idea o time?
     
  23. alhbln

    alhbln Formula 3
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    p.s. if it's only the odometer acting up temporarily, try exchanging the BC327 transistor and the 680uF capacitor between the odometer coil and ground.
    Another defect leading to the symptoms you have described might be a broken winding within the odometer coil. A multimeter set to resistance/ohm would show an open connection if there is indeed a broken coil wire.
     
  24. Nickt

    Nickt Formula 3

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    I did replace the BC237 when I changed the IC. I noticed that the speedo needle was very very slightly pulsing at idle. just slightly twitching. It might have always done that buy I have never looked that closely.

    I will get some more MC237s and change the capacitor. I guess I could make the protection circuit, but that's a waste of time if the IC has blown already.
    I don't think its the coil, as it did work perfectly for 1.6 miles after the IC was swapped over,
    The old IC moved the odometer .2 miles over about 200 miles, so I guess something in the IC was still working

    CHEERS
    Nick
     
  25. alhbln

    alhbln Formula 3
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    Ok, you're in ;) 2-4 weeks including the PCB production should be realistic. Send me your mail address via PM please.
     

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