Need help testing MS1 V3.0 spark circuits on $2015 Miata

[MrJoshua]

Hi all,
We have an old MS1 V3.0 on a GRM Challenge turbo 91 Miata that has been on the car for 7 years running fairly well despite severe neglect. We recently lost spark on plugs 2&3. There were a few possible causes of damage to the MS-I was building a COP setup using a gutted stock igniter and accidently arc'ed the 12V+ twice. We also had the key in the on position for a fairly extended amount of time which I understand leaves the coil and igniter "Charged" and can cause overheating. We tried replacing the igniter and coils with presumed good stock parts and were unable to fix the problem. The car had to go back to its owner in Georgia so I pulled the squirt and took it with me back to Florida. Sorry for the wall of pics and links that follow. Thanks in advance for any help.

The GRM discussion is here:
https://grassrootsmotorsports.com/forum ... 095/page1/

The board seems is built similarly to these instructions: http://www.diyautotune.com/tech_article ... _miata.htm

With these ignition mods:


Here's the front:


Here's the back:


Here's a stressed looking component:


Here's the old stim I'm using with an 8.5V 550ma power supply (used 9v at first) :


I followed Matt's advice and link to test the Injection circuit (due to the melty component above): http://www.diyautotune.com/tech_article ... ooting.htm

I made an exciting video using LED's to test the spark circuits:
http://s61.photobucket.com/user/Sloshua ... t.mp4.html

Any help you guys can give is greatly appreciated.

[Matt Cramer]

Try removing the CPU and applying 5 volts to pins 7 and 8 of the CPU socket. Do the LEDs come on?

[MrJoshua]

Try removing the CPU and applying 5 volts to pins 7 and 8 of the CPU socket. Do the LEDs come on?

Matt-I hope this is what you were looking for- I removed the CPU, plugged in the Stim and used the 5V pin in the proto area as my 5V source:

5V to pin 7 doesn't light anything:


5V to pin 8 lights up the LED farthest from the DB9:


Are those the LED's you are looking for or are you wanting me to use the LED's at the points I used in my test video?

[Matt Cramer]

That's what had in mind. It sounds like Q6 has failed.

[MrJoshua]

Thank you Matt.

I have these from an unbuilt kit:


Should I just replace it and retest?

Is there anything else I should test first?

[Matt Cramer]

Yes, I'd just swap it out. It's already failed a test.

[MrJoshua]

Replacing Q6 made the LED light up and the external LED test get identical results on both channels. Thank you Matt! Is there any other test I should do before I reassemble it and mail it to Paul so he can put it on the car?

[Matt Cramer]

While I'd prefer to test the whole thing with a JimStim, I think we've gotten as far as you can with available equipment.

[MrJoshua]

Decided to build a backup squirt out of the kit I've had for years for redundancy but I ran out of parts. Need a TIP 122 for idle control and a .1uF capacitor used for the "cap mod" described here: http://www.diyautotune.com/tech_article ... _miata.htm that is used to quiet a noisy ignition signal.

So I guess that actually leads to a couple of MS questions:
1) I have a BIP373 I am not using. Is a BIP373 a reasonable substitute for a TIP122?
2) I have 2-.001uF 100V caps, 1-.01uF 50V cap, and 1-.22uF 50V cap.
a) Can I make something resembling a .1uF 50V cap out of those?
b) How much capacitance do I really need to quiet the signal?

Bought kit to build a JimStim as well so I can test things more thoroughly in the future.