This is probably beyond my repair ability. Any idea where I can send my cluster out to get fixed. I was preparing my FD to get it listed for sale then of course the dash quits working. I have no working tach, speedo or odometer. This will probably make it difficult to sell.

I've attached a couple photos. Any suggestions would be helpful. Thank you.

Joshua


If you post some photos of the speedo board then I may be able to help. Use the zoom function or get in close to take pictures of the suspect areas on the board. I also need you to provide more information: what specific components did you replace? Did you replace them or did a solder technician do it? Do you have any prior experience behind a soldering iron?[/QUOTE]

 

@danwatson64,

I combined your thread with this one. There is a lot more relevant info to be referenced here. When able, read through some of these posts to better understand some common problems with these boards.

@3rd-Gen-Rcr,

Take a look at previous posts in this thread. You have the classic symptoms of leaked electrolyte from several capacitors. If you believe this repair is above your level then you can seek out other members - @zensation may be able to help. You may want to send a PM to him. Otherwise, these components can be replaced with some basic soldering skills. I see you desoldered the speedo motor so that's a good start. What does the back side of the board look like?

 

[/QUOTE]

Thanks Gen.......I can help if you want it repaired quickly.

 

Thank you for your help with this. I went back through this thread and read a through a few recent pages. It looks like there are a lot of people on this forum that are pretty bright. I feel a lot less intelligent after reading it now.

I'm ok with basic repairs and de-soldering and re-soldering some of the bigger stuff, ie the speedo motor. But after seeing all the capacitor juice all over the board I feel like most or all of these components should be replaced. I ordered a bunch of capacitors that came in yesterday but none of them look like the ones on my board. I got the list of capacitors to order for this project online somewhere but not this form.

The back of the board (green side) doesn't look bad at all. Just the usual dirty solder points that I cleaned up with some alcohol but nothing like the business side of the board. Unfortunately, I got frustrated with it yesterday and just put it all back together to ship somewhere before getting any more photos.

Another issue I have with this is I have such a lousy memory that I can never remember how to put things back together correctly. I think I may have put some screws back incorrectly and I ended up with 2 left over that I couldn't figure out where they went.

At this point I don't want to risk screwing up the cluster any more than it currently is. I would rather get out the checkbook.

 

Thanks Gen.......I can help if you want it repaired quickly.[/QUOTE]

Yes please!
Here is my contact info.
Joshua Abel
ABELexpress LLC@yahoo.com
412-526-0585
I can get it packed up today and shipped out tomorrow.
thanks a bunch.

 

let me first say thank you for all this great information, while I haven't read everything yet. It has helped immensely.

So my cluster worked fine from my JDM 92 FD, apart from the odometer readout.

Upon pulling and desoldering I can see leakage from capacitors and several parts look to be burnt out.
C1, C2, C3, C9
Z02,Z03, Z04,Z07
Tr2,Tr7,Tr8
Da2

Just wanted to know the best course of action, would I be able to remove the replace all the capacitors assuming the zener diodes and other parts are still working?

 

Trying to resurrect a dead speedo.This instrument cluster had a dead speedo and tach .Speedo odo did not light up and speedo needle did not move. The tach does work with a different speedo.

I did replace most all the caps except C15 with the part no.s in the thread on speedo parts. DA2 had a leg broken which I sourced from the one listed in that thread ( an ebay link )as that was the only source for that part. I looked for damaged traces but only found the common one that C3 takes out and repaired that trace as in the picture.

This exercise yielded a speedo that lites up the odo and the odo increments km's but the speedo needle doesn't move.

Looking for direction on what to look at next. When I did desolder the needle motor I did carefully try to remove the motor ,but I guess one leg was still partialy stuck and resulted in pulling on the associated pin. When i noticed it was pulling the pin out I stopped and desoldered it and pushed the pin back up.lt looks like it wasn't a fixed pin but I'm not sure as i was carefull when trying to lift the motor off the circuit board.

 

just seeing this. if you still need help i offer a rebuild service. pm me if ya like.

 

Spy shots of a digital stepper motor tachometer replacement ive been developing. Sweeps great here's a link to a video of the function in the cluster https://vimeo.com/manage/videos/788159605

 

That is pretty cool. It could help solve the dreaded tach failure issue. How do you convert analog input to digital stepper motor?

 

it probably fixes more issues than you think. Since 2015 I've repaired about 800 or so fd gauge clusters for people and the only inoperable issue that cant be repaired is a destroyed gauge motor. Luckily I probably have the largest supply of spare parts for these clusters at least in the USA so I can replace if needed but when those parts run out there's not a solution. I got a quote from an analog air core motor manufacturer to make a direct replacement motor if I reverse engineered it and they wanted a $500k order so obviously that ain't happening. Then I had the idea of replacing the motor with modern gauge steppers like most gm models use since I knew they were cheap and easily sourced. All that was left was for me to re design the tach board to take the incoming signal and convert it to digital steps. So it's a new circuit board I designed.

Also on top of fixing the obvious issues with the oem tach, it also fixes stuff that Flys under the radar. For instance when I was doing some calibration a while back for new gauge faces I realized how absolutely horrible the consistency was between tach assemblies. The images below explain what I mean. I have several tachs I use for testing and what I did was make a calibration template that I can use to determine how precise a tach is. I drive the tach up in increments of 33hz on a function generator on my test bench. Then I can mark the needle location and measure the angular gap between increments. In a perfect world each 33hz increment should retain an identical angular gap from the last mark. This denotes an accurate measurement on a gauge face. I.e. if every 1000 rpm increment on a gauge face is say 30° apart and say 33hz represents 30° of travel then every 33hz increment should correspond to 30° spacing. However in the pictures below you can see the spacing varies from 19° to 36°....this will never read accurately despite being otherwise fully functional in the vehicle otherwise. This digital version is fully calibrateable and opens up a world of opportunity especially for people that want say an 11000 rpm tach.

 

Super nice work. Thanks for sharing the details.

 

Thank you. You can check out pics of some of my other work here www.rxclusterworx.com

 

Anybody got the voltages for pins X1, X2, Y1, Y2 on the stepper motor when the speedo board is powered on? (Not while counting just powered on). I'm getting 5.5v on X1 and 10V on the other three.
Problem is when I apply more than 137Hz (marks about 60MPH at this frequency) the needle goes back to "0". I just want to find out if my signal generator is bad or if there is something wrong with the driver or the motor itself.
I have repaired traces and replaced almost every part there is to replace on top of board except the 4 chips and diodes and resistors that measured "good".

 

Dont know if anyone monitors this thread anymore but I cannot get my speedometer to work in the car. I have searched and read countless post and absorbed as much information as I could from all the great information found here. First a little history, the car has sat for probably 20 years or so before I recently started bringing everything back to life. One of the first things I actually did to the car was fix the odometer using the information found here so I could get actual mileage for getting the title in my name. I was successful in making that repair by replacing all the caps mentioned and reflowing solder to a couple ICs. This was probably 8 years ago at this point, The issue now is that since I have the car all back together and driving the speedometer is not working. I followed the procedure in the body electrical manual, I put car on lift and in gear with wheels turning testing for voltage at the plug and it was like 2-3 volts generated by the speed sensor at a low speed. This seems ok for the speed of the wheels at that time. So I suspected the speedo board has an issue and removed cluster again for inspection, nothing obvious was found (I can post pictures later). I ended up purchasing another speed sensor that outputs the same type of signal so I can bench test the speedometer outside the car. I powered the board and using a drill to spin the speed sensor generated a signal which I applied to "speed sensor B" pin on the board and speedometer works here. I can vary the drill and make the speedometer go up and down smoothly, the odometer also counts as it should during this time. So it seems my issue is in the flex print or a bad connection between plug and the flex print for the actual speed signal. Every other function of the gauge works fine, I have a power fc and datalogit so I was going to hook that up and see if I have speed there. I do not have the commander unfortunately which would probably be easier to deal with. Anyway, I will try and document what I end up finding and if anyone has any advice Id love to hear it. I had reached out to Zensation via his website but it seems he is in the middle of a move and I havent received a response yet. Have a great day everyone

 

Here are some pictures of the board as it sits currently, last night I verified again the speed signal coming from the transmission with the car on the lift in various gears producing voltages from 0.5 VAC in first gear idle to about 3.5 VAC in 3rd with some throttle. I did not want to get the wheels spinning much faster that that but it does verify everything from the speed sensor to the plug (C1_01_03 pins 3A and 3C). The Zener diodes in the second picture I am currently trying to reflow, I used a solder sucker to get what I could out and went back with electronic silver solder. I do know the stepper motor is ok because I applied a test voltage to "speed sensor B" pin while putting 12v to Illumination and grounding at PGND. This would vary the speed smoothly with the drill input. Ill keep at it I suppose.

 

You might want to look at a video I posted in this topic on another forum: https://mazdarotaryclub.com/forum/in...?topic=85243.0

I have been working on a couple of FD clusters to understand how they work and to build some test circuitry. My intention is to understand them enough to be able to repair them. Information on this rx7club forum has been invaluable, for which I thank all contributors.

A common failure mode I have discovered is with the chips that drive the air-core gauges. You have pictured one such chip, AN8363, which drives the speedo gauge. These chips are failing and I have proved this on 3 chips now - by applying a heat gun I can get them working temporarily. These chips are obsolete and I'm still working on a way to replace thir function with an alternative chip, or an Arduino controller based solution. More details are on the topic link.

 

Just to close out my issue, it ended up being the speed sensor in my case. I was under the impression that since I was able to measure about 4 volts and it would raise and lower with wheel speed that my sensor was good. The FSM states it needs to be 5 volts, so lesson learned.

 

I had a cluster brought to me with a blank odometer. The CPU board had already been recapped a year or so back, to solve another issue, so faulty caps were unlikely to be the problem. Everything else on the cluster was fine.

I did some probing with a 'scope and noted the OKI display driver chip was sending an (active, digital) "OFF" signal to all the segments, suggesting the driver chip and display were probably OK and the problem might be with the input to the OKI chip. The serial data input stream to the OKI chip comes from the NEC 4 bit microprocessor (CPU) - bad news if that was at fault!

Power to the CPU was good, looking ominous. Checked the "XTAL" 4.19 MHz ceramic oscillator that connects to the CPU to provide a clock signal for the CPU to operate and bingo - no output (a sine wave should be present on one of it's pins). Luckily, I had a cannabilised spare so swapped it out. Powered up the module and the odo was now working fine.

So, an unusual fault, but if anyone has a blank odo, check for a sine wave on the oscillator ("XTAL", crystal)component.

One happy owner collected his cluster today.


location of failed "XTAL" ceramic oscillator

Odo now working perfectly on test box.

 

I repaired another cluster today (I'm based in the UK). Fault was a no-responsive tacho. On dissembling the cluster and testing the tacho itself, it turned out to be working fine. Further investigation on the main board under the speedo (which processes the tacho signal from the engine) revealed a failed TR8 (type C133) AND a PCB trace fault - a PCB trace below IC4 on the main board had, seemingly, corroded into dust, out of sight under IC4. See pic below of the green deposits on 4 pins of IC4. The corrosion deposits were carefully removed with a swab and isopropyl alcohol, which shows the IC pins themselves were clean, intact and not corroded, pointing to the deposits most likely being the remains of the copper PCB trace..

TR8 was replaced and the missing trace bridged out and the tacho is now working fine. Cluster re-assembled and tested and all is working to spec.

Published here in case it helps anyone else diagnosing faults on these 20+ year old clusters.

Horrid green corrosion deposits on the lowest 4 pins of IC4. The dusty remains of a missing PCB trace under IC4!

Missing trace bridged under the PCB.

Failed TR8 (which drives the tacho module) after replacement

 

Hi Casey_uk,
Couple of questions on the TR8 transistor.
1) Did you measure TR8 out of circuit with a multimeter(in diode mode)? How did you conclude it was faulty.
2) The original TR8 is a "type C133", is that BC133 as I haven't heard of a C133 before.
I have an intermittent tacho(always on 0rpm & if driving for over 30 mins/warm weather will begin to work flawlessly).
I put a CRO on the TAM wire/connector(cluster connected to car), got a good PWM signal but nothing on the TACH screw, which strongly suggests the circuit around TR8/IC4 is faulty. My TR8 measured open circuit(on diode mode) between base/collector & base/emitter.

 

Hi Ljay

Re:
1) TR8 was base-emitter short, so easy to identify in circuit.
2) Apologies, a typo, should have been C144 (or 2SC144, DTC144) an NPN transistor with built-in bias resisitor. I bought 20 from AliExpress for about £2. Typical datasheet attached.
3) Your tacho symptoms sound like a failed air-core gauge driver chip, of which I have seen several (scroll up a few posts to see my comment about them). Chips will work with heat-gun applied.


Chips are obsolete, but chips with the same function are available. They are not pin-compatible, so require a replacement PCB at the back of the tacho. OR, replace with a micro controller of some sort. I have a prototype of this using an Arduino controller that I am still developing. I'm also working on replacing the air-core gauge with a stepper motor, driven by an Arduino (more reliable and more accurate)

 

Thanks for the quick reply Casey_uk, I'll compare specs of that transistor to the one I put in, but i think its a basic NPN transistor. Do your replacement DTC144E measure like a normal NPN would? If mine is open circuit I would imagine I would have a dead Tacho always, yet after replacing with a substitute NPN, I'm still with an intermittent tacho(well sort of...when I put cluster back in car I wouldn't say it was warm & it worked on/off, then I ran out of time to do any more due to lack of light).

I have viewed your YouTube video previously & it looks ominous to my fault, however if that is the case, then I would imagine that I would still have a signal at the Tacho screw, which I don't.

I purchased a cheap PWM signal generator so will hook it up to the tacho board when I get a chance(as per another thread) & I guess that will reveal more. propose to put some heat on that IC like you did.

 

Yes, testing the tacho with a fixed pulse width source in the frequency range 1Hz to around 300Hz will enable you to test the tacho independently. The pulse width should be around 1.5ms, but I've found that is not critical.

If that checks out OK, you ideally need an oscilloscope to look at the signal going to the base of TR8. That's more complex, as you need to power up the CPU board and supply a simulated VSS signal to the board - a sine wave passing symmeyrically through 0v, with peak to peak value of around 9 volts, frequency 1 to 410Hz.

if no signal at base of TR8, which was the case with the board I recently repaired, you work back logically through the circuit, looking for where the signal gets lost. The 8 pin LM2903 SMD Icomparator IC is key to processing the sine wave and converting ito a digital signal to the base of TR8. Note TR8 is open collector, so will need a pull-up resistor if not connected to the tacho board to see a output at the collector.

interested to hear how you get on.

 

Forgot to add. The C144 ransistor doesn't work on a standard, basic transistor hfe (gain) tester. At least they don't on mine!