Miata 'Joes better spark mod' mistake. No spark A output

[okisub]

Hi,
I'm in a world of hurt here, hopefully someone will have a suggestion that can save my bacon.
I am in the process of building a MS2DIY for my 1989 MX5 using this guide: http://miataturbo.wikidot.com/ms2-a
But when building I forgot one of the pull up resistors on the spark circuit, causing one of the transistors to blow:


After changing out the blown transistor and adding the missing resistor I did a spark test in the car and only spark B is firing. If I swap the trigger wires on the coils the other set fires, so I guess they are physically OK.
Next I replaced the other mod transistor, Q6 and Q8 even the D14 and D16 LEDs and checked resistances of R24-29 and mod resistors but no good.
With the daughter board removed comparing the outer legs of Q6 and Q8 I get different readings -Q8 open and Q6 shorted.
Both R24 and R28 show 5V when the MS is powered up, beyond that I don't know what to check.
I've also been over my soldering with a 10X loupe and there are no bridged traces on the top or bottom of the board anywhere.

What should I be trying next because I'm out of ideas?

[prof315]

The build instructions found in the manuals linked at the top of the page are what you should have used. Google and other search engines that lead you away from those are NOT your friend. The BEST way to do logic level spark outputs is the TC4427 FET method shown in the manual.

As far as your lack of spark A, the different readings on Q6 and Q8 suggests that one of them ( probably Q6) is bad

[okisub]

The build instructions found in the manuals linked at the top of the page are what you should have used. Google and other search engines that lead you away from those are NOT your friend. The BEST way to do logic level spark outputs is the TC4427 FET method shown in the manual.

As far as your lack of spark A, the different readings on Q6 and Q8 suggests that one of them ( probably Q6) is bad

OK, I've emptied the proto board and ordered a TC4427AEPA, resistors and fresh Q6,Q8 transistors. Hopefully they will solve the problem.

[rickb794]

I don't understand the build in the injection circuit flyback dampening has been left out but PWM current limiting is installed.

A different transistor has been installed in Q7, if this is an ignition out it should match the other channels

Something strange has been done to the serial connection. Is that bluetooth or USB?

Yet the clock parts for a MS1 processor ARE installed.

I don't think leaving out a pull up resistor would blow a transistor, I would suggest you have an external wiring issue.

Do you fully understand what you are trying to accomplish or are you blindly copying what someone else has done?

It might be best to describe your hardware setup.
Are you doing COP?
Do you have high or low impedance injectors.
Is this a V6 or a I4?
Are you aware that USB cables can make a serial connection on a running car almost impossible? <ignore if you have installed bluetooth

I can't see if there is an insulating spacer under the nut on your Fidle mod output.

[okisub]

Thanks for looking my build over Rick.

A different transistor has been installed in Q7, if this is an ignition out it should match the other channels

The change of Q7 was part of the mod at http://miataturbo.wikidot.com/ms2-m to run the fan relay -this is working correctly if I force it on in Tunerstudio.

Something strange has been done to the serial connection. Is that bluetooth or USB?

That is a bluetooth adaptor, it has been switched off the whole time because I've been using the serial connection in the car to try and simplify things, until it's running properly.

I don't think leaving out a pull up resistor would blow a transistor, I would suggest you have an external wiring issue.

I have checked over my harness quite a few times in the last week and I'm certain it's correct.

Do you fully understand what you are trying to accomplish or are you blindly copying what someone else has done?

I have been following the miataturbo guide to the T, which has worked for many many others.

I can't see if there is an insulating spacer under the nut on your Fidle mod output.

The Mica spacer and bolt insulator is under Q4. The multimeter shows an open circuit between the top of the TIP122 and the heatsink.

Are you doing COP?
Do you have high or low impedance injectors.
Is this a V6 or a I4?

The car is a 1989 Mazda MX5/Miata with a 1.6L I4
I'm running the stock Mazda coils, twin coil wasted spark setup. Both coils are working on the stock ECU and both can be triggered with spark B (off D16) in test mode if I swap the trigger wires at the coils to test.
The injectors are new Flow Force 640cc which are high inpedence. Product link: http://www.flowforceinjectors.com/produ ... -kit-miata

The parts are due to arrive today, so I will follow the '5.3.1.3 Logic spark outputs - FET driver method' from the official manual and see how we go.

[okisub]

Just an update:

I fully redid the ignition circuit as laid out in the manual with the TC4427 etc and we have spark!

Although I'm sure the design of the miataturbo mod works, I had done something wrong and just starting again with this even simpler design got me through.
Thanks again for the help guys.

And now onto the next thing -a sneaky vacuum leak. But that a question for another forum.