Testarossa Odometer Not Working Advice?

sorry, have not read right before
still in hospital and take a lot of medication

 

The RCA 92967 was an OEM design for Marelli and was never available for the public unfortunately. THE RCA IC processes the gearbox sender signal and creates a mixed (PWM with an DC part) output signal feeding the base of the BC237 transistor driver. There is an additional circuit in the 92967 to adapt the ODO motor speed to the input voltage to make sure the displayed speed is independent from battery/voltage fluctuations. Pretty nifty design for the times.

To determine if the RCA is broken i would recommend to first check the square wave input signal on RCA pin 1 (yellow trace "In") coming from the gearbox sender, and then the ODO motor transistor driver output (cyan trace "ODO out") on pin 5. If the cyan trace looks good then the problem is most problably either with the BC237 transistor driver (check the BC237 collector output).


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Thanks for your kind response, Adrian. I don't know if Mike has an oscilloscope to check these waveforms and it would be difficult to monitor them with the car in motion. It may be best to simulate a speed signal on a test bench. If not possible, then it may be more practical just to change the components he can find (and hope for the best).

Sorry to hear that Romano. Get well soon!

 

thank you
had an accident with my small motobike in thailand on the 2nd january, the other went away. left arm broken, could not get operated because they tested me covid positive. so had to wait until last friday for operation. also right side chest 4 ripps and left side chest 6 rips broken

 

Sorry to hear about your accident Romano, wishing you a speedy recovery!

I can confirm the Speedometer is working just fine, so it won’t be the speed sensor…

Thank you for your help and replies - Ian & Adrian, much appreciated… unfortunately I don’t have an oscilloscope so won’t be able to test or simulate, so going to pray it’s one of the other more readily available components which are broken. So will have to hope for the best it works after the repairs…

I also managed to track down that 92967 IC was made by Harris Semiconductors, eventually they were absorbed by part of the Japanese Semiconductor company Renesas.

Will try hunting down any data sheets and even any spares if they exist too.

 

Simulating the sender signal is easy, have a look at the last image on the Veglia speedo sender page, its basically a square wave 0-7 volts peak.
366 Hz should display 100 mph/160 kmh on a (non turbo) Type 2/3 speedo.
http://www.dinoplex.org/instruments/vegliaspeedosensor/

Good recovery and all the best! It is quite an unfortunate time to end up in a hospital. Alles Gute, ich drück die Daumen!

 

An update from today. I have now replaced nearly all the ICs, capacitors and transistors on my Odometer, also cleaned up the mechanisms and used silicone grease on the plastic gears etc.

The only IC I have not replaced (yet) is 92967, after extensive enquiries to semiconductor sources globally I have actually found a supply but at a cost of $750 each!

Now that my odometer is back together again, is to try it in my Testarossa. If it still doesn’t work I’m looking at either obtaining a donor Odometer, buying the IC or just leaving it be…. But before I can try it, is to get the alternator replaced out and the heater hoses too

 

Hi folks another short update. I have finally managed to track down an alternate more price friendly supply and purchased 5x of these unicorn 92967 RCA 606 ICs…. Hope they are the genuine items.

At least if worst comes to the worst I can replace the 92967 IC in my odometer, as there is not a lot else to change apart from resistors and diodes (but appeared to be ok on testing)…

Will provide a further update soon

 

There will be folks queuing at your door soon (or will you give us your source?)

 

Im hoping these are the real McCoy and do arrive, coming from the Far East…. See what happens first of course you will have first dibs if they check out

 

Note that these chips are also found in some Ferrari speedometers (not sure about the TR)

 

That’s what I understand too like the Ferrari Mondial, also Alfa Romeo’s…

Fingers crossed

 

My 91 Testarossa's odometer keep advancing when the power is on.
https://www.ferrarichat.com/forum/threads/odometer-keeps-running.584869/
The chip on my gauge is 92967 H036, also not able to source.
Wondering what is the difference between the two.

 

Looks like the IC that Mike found (made by Harris). The 036 number may be a Harris date code.

 

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That is correct the H is indeed for Harris Semiconductor…..

I’m not sure if the 036 is a batch code or IC variant. I.e. KMs or Miles?

@spaceship is your Odometer in KMs or Miles? My one is in KMs?… I am not 100% sure if that makes any difference on the 92967 IC or not…

if and when these ICs turn up, will report back and I may be able to supply some….

 

Thanks Mike! My odometer is in KM.

 

OK then the 92967 ICs I have ordered should be a perfect replacement....

 

They have arrived today! ….. 92967 ICs
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so then start working

 

fingers crossed, need to sort out the leaking coolant heater hoses first …. Getting worse
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As a follow up and after 3+months of my car having various work done, such as radiator rebuilds and major service etc. I am happy to confirm the Odometer now definitely works

So the new replacement new 92967IC and other proactive electronics replacements have worked.

If anyone needs a 92967 IC which is rare as hens teeth, I have a few available

 

Congratulations!
It will be great if I can have one, my odometer is not functioning properly. Thank you very much!

 

Hi Mike, wonderful news!
I am also looking for the 92967IC. I would appreciate it very much if you could help me out with getting one too!

Looking forward for your reply.

 

Hello.

Thanks for your message, private message sent.

Best Regards
Mike