You legend, replacing those two caps worked!

Cody, glad this post helped fix your odometer.

Would you share any additional insight, problems, experience, or identify which caps were replaced?

Cheers,
George

Just a comment for all you guys that have issues that keep coming back... My speedo & tach were intermittent (after already changing the caps on the tach) The fix I found for both was in cleaning the contacts on the plastic circuit board on the very back of the cluster. The connectors were not making good contact with the plastic tabs in the square holes. You can inspect the connectors themselves for pins that may not protrude out like the others on the same connector.

Gyan,

Well said! That happened to me once before. Cleaning the contacts with isopropyl alcohol and slightly bending them outwards would ensure a proper electrical connection to the wire harness.

Needed to replace other components in mine
 

My first post here.

First of all, thank goodness for this thread, so helpful, I commend all those who have contributed.

Car: 94' R2, completely stock except for a mildly lighter flywheel and street clutch. Silicone vac hose fix has been done. 79k original miles.

Spent the last few weeks trying fix my faulty odometer, finally successful. It turns out that the two caps plus other components in mine were also bad. I believe this may become more common as the cars get older and suspect the leaking cap electrolyte tends to corrode and kill parts in its path as it spreads across the board. Bad components were identified by probing with a multimeter in 'diode' and 'continuity' mode, removing the suspect component and re-probing with the part missing. since the shorts went away with the missing components, the assumption was the components were bad.

Bad components:

- Two caps already exhaustively covered in this thread
- ZD3 had one leg corroded off, no contact at all (replaced with 5.1V zener diode, I could not find confirmation that the value was correct, see ZD5)
- ZD5 was shorted (0 ohms) (also replaced with 5.1V zener, determined zener voltage by removing good ZD4 and testing it with a power supply)
- TR7 shorted between E(mitter)-pin and middle(base)-pin (replaced with NTE123AP transistor, cross reference from C144 printed on component)

After replacing everything, the odometer back-light suddenly didn't work, which sent me on another probing adventure only to find bad bulb contact. This was only after mapping out the entire flex circuit board on the back.

Success! odometer and backlight fully functional after an embarrassingly long time.

Side note: Before the fix, the car started to idle poorly(hunting and dying) and threw a 'speedometer sensor' code. All gone now. Most likely the signals to the computer were getting dampened or noisy due to the shorted components. Passed smog here in CA with flying colors.

I can post some pics of notes and components if anyone is interested.

-GE

awesome info.. mine is still intermittent after replacing the cap, but as you can see in the pics my ZD5 and the ones next to it look bad too. first i will try cleaning the connector contacts, then the 5.1V zener replacements next. thanks!

interesting note.. replacing the cap zero'd my odometer mileage somehow

I recommend to probe across the diodes and transistors from the back side of the board before replacing. You can do this with a cheap multi-meter from harbor freight. It looks like there's a harbor freight near you: Harbor Freight Tools

It's a great $6 investment, sometimes they have coupons for a free one if you buy something for $5. The diode function can tell you if the diodes and transistors have reasonable readings before you remove them. Probe in both directions, looking for a reading of 0V or almost 0V in one or both directions. I can write a better walk-through if useful.

Odd that your odometer zeroed. Maybe something shorted caused this. Maybe when the faulty component is replaced, the original mileage will come back? Just guessing. The mileage is stored on a chip described at length in another thread.

-Greg

Subscribed for reference, i never find this when searhing

https://cimg6.ibsrv.net/gimg/www.rx7...df8d47b13.jpeg

https://cimg7.ibsrv.net/gimg/www.rx7...fa30eb503.jpeg

https://cimg8.ibsrv.net/gimg/www.rx7...613b12f78.jpeg

Anyone know what cap this is? It says TR8 on the board but nothing on the peice itself. It's the one with burnt connections and a broken wire.

That is not a capacitor! No capacitor has 3 legs. TR8 looks like a power transistor. Can you still make out any part numbers on the transistor? If so, then google it and see what comes up. You can also try digikey or mouser (.com) in order to narrow it down. If you cannot see the part number, see if there is a similar TR(x) on the board for a part number. I would also replace the associated electrolytic cap next to TR8. it is a 2.2uF 50V cap that can be easily found on digikey or mouser.

Additionally, take a q-tip with isopropyl alcohol to clean up the (brown) flux stains on the board.

One Oh-by-the-way, take a look at post #130. Svgalib said this:
- TR7 shorted between E(mitter)-pin and middle(base)-pin (replaced with NTE123AP transistor, cross reference from C144 printed on component).

Make sure you check the top and bottom of the board for any other damage such as burned solder runs or damaged eyelets.

GE,

Do you still have photos of your work that you could post? Do you still have the part numbers for ZD3 and ZD5? Have you any problems since the repair, such as loss of ODO for a bit and then reappears? Thanks for sharing the component replacement list, especially TR7.

Thanks,
George

I cant read anything on the transistor unfortunately. I will look closely at others. I did find these at Digi-key but have no idea which to purchase at this moment.
Transistors - Bipolar (BJT) - Single | Discrete Semiconductor Products | DigiKey

Thanks for your help.

TR8 Transistor 2N5551

these look more like a match visually

Does anyone have a photo showing the part number for TR8 or have their speedo board disassembled? Perhaps someone could verify it for silverTRD? I doubt I have any good shots of it but will double check.

*break*

silverTRD, you're welcome for the support. It is important to verify the correct part number for the transistor. Just because a transistor physically looks like the bad one doesn't mean it is the correct replacement part. I'm sure you want to fix the problem quickly but don't make haste in ordering the (wrong) part. That may lead to unnecessary work or worse - additional damage to the board.

Will you be replacing the component yourself or know someone locally who could desolder the bad transistor then solder in a new one?

I wish you the best of luck in the repair!
Cheers,
George

P.S. I do not have any additional photos that may show TR8 from my photo archive.

TR8 is marked C144 with ESD below it. It has no markings on the back.

^Thanks for the confirmation, dgeesaman! I'm sure that silverTRD appreciates the update too!

So TR8 is the same part number as TR7. Therefore, part number NTE123AP is an acceptable replacement.

I will be tackling this myself. I replaced a couple of the caps already for practice. It wasn't as difficult as I thought it would be. I need a new 2.2Uf and whatever transistor tr8 is

Thanks to the both of you for your help! I'll update this thread when I make the repair. I also have some extra 1uf,10uf,47uf, and 1000uf if anyone needs some.

Glad to see someone gave us the voltage of the zener diode.

However when I go to digikey there are literally hundreds of parts with that voltage.

Do you have a part number of the diodes you replaced with?

This has been something I need to replace on my board also.

I asked an electronics guy about it, and we talked about the wattage needed. He said that the wattage just needs to be higher than what is required or it will get too hot having one with more watts is always better and won't impact it. Granted the bigger the watts the bigger the diode it seems. heh. *edit* nm they are through hole been awhile since I looked at my gauge relooked at some pictures on page one.

Either way if anyone has the part numbers that would be super helpful.

Also to note that these being zener diodes they also have a reverse flow voltage. Knowing this is important too, but the parts on the board have zero markings on them from what I can tell.

kyle15,

The Zener diode that svgalib replaced isn't a surface mount device. He should be able to give you a part number for it. What Zener diode do you need? What else must you replace to get the odo back up? Feel free to post some pics too.

Ya I know. I just realized it was through hole. I need to know what part he used. I need to replace the same zdiode numbers he did. I edited my post to take out the surface mount part heh.

I have been looking at these. These are all 500mw max power.

They all slightly vary in
Current - Reverse Leakage @ Vr
Voltage - Forward (Vf) (Max) @ If

they also vary slightly in
Impedance (Max) (Zzt)

I am not worried about the operating temps as they all seem acceptable.

Here's an update: I got it all back together and the speedo still doesnt work unfortunately. My mileage is stuck at its current mileage. The tach also doesnt work but I suspect that may be the signal wire issue. I looked thru the whole circuit board on the speedo and cant find anything that looks burnt or out of order. :headscratch:

Has anyone ever had issues with Resistor R10 ? I took a pic of my good JDM speedo to figure out the exact specs . I can make out it's 20 Ohm and J ( 5% tolerance ) but I can't figure out the wattage rating . It says 62 or 6Z . Does anyone know the details of this part ? On my faulty speedo it's got some black burn marks on it ( gonna measure tonight if it's faulty ) I have done a visual inspection of all components and this is the only one that stuck out with a suspicious mark .