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Old 06-16-2016, 11:16 PM   #1
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Default MS3X help. No 12V at U5

I'm at the step of checking voltages of my MS3 build. I have 12V into Pin 28 and GND to Pin 1.

I do not have 12V at pin 40 of U1 and I do not have 5V at the proper places at U1.

When I traced the 12V line I was able to follow it and I do have 12V at IAC1B, JS1 and pin 37 of U1.

I do not have 12V at U5. I've checked the diodes and they all look to be in the proper orientation. I do not have 12V at any of diodes D10-D13 which has me confused....


Any ideas of whats going on or what to try next?










Attached Thumbnails
MS3X help. No 12V at U5-80-capture_58303e276013f5879cd5c68f60585282cd31d421.png   MS3X help. No 12V at U5-80-img_1085_9fe4031e0f86766234d59cd04cc761ab1527b08f.jpg   MS3X help. No 12V at U5-80-img_1084_203c7b10c158678e3cecced931a9c2dcecc70384.jpg   MS3X help. No 12V at U5-80-img_1083_502a76c1b6265ee33fb2fa35b593757e8f1f8d8f.jpg   MS3X help. No 12V at U5-80-img_1087_5005d23e8bb0751892eb5b54843dfb00179519cf.jpg  

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Old 06-16-2016, 11:29 PM   #2
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I meant to put this in the Megasquirt Sub-thread. If a mod could please move it I'd appreciate it.
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Old 06-17-2016, 09:47 AM   #3
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what writeup are you using to build your MS? You've added a ton of parts you don't need and didn't mod it for miata inputs yet.


if you dont have 12v at U5, then the problem is a trace on the PCB, 12 goes directly into PIN 1 of U5 from the DB37 connector. Look at the bottom of the board and look at the thick trace for it -- it also hits the middle pin of both the Q9 and Q12 FETs you didnt need to install.
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Old 06-17-2016, 10:11 AM   #4
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To check for a short in the Megasquirt PCB, power up the Megasquirt on a Stimulator or on the car and check the following points for voltage with a multimeter.

You should find the same voltage as the battery voltage on the following points: S12, S12C, the center legs of Q9 and Q12, the left (non-banded) end of D3, the left leg of U5, and the left (banded) end of D9.

You should have 5 volts at the following points: S5, the two +5V holes in the proto area, the right (non-banded) end of D9, the right leg of U5, the left (banded) end of D19, and pins 1, 20, and 31 of the CPU.

Let me know where you find the correct voltages, and where you find the wrong ones
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Old 06-17-2016, 11:23 AM   #5
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Quote:
Originally Posted by Braineack View Post
what writeup are you using to build your MS? You've added a ton of parts you don't need and didn't mod it for miata inputs yet.


if you dont have 12v at U5, then the problem is a trace on the PCB, 12 goes directly into PIN 1 of U5 from the DB37 connector. Look at the bottom of the board and look at the thick trace for it -- it also hits the middle pin of both the Q9 and Q12 FETs you didnt need to install.
I've been using the official MS3X v3.0 manual. Could you please link the recommended miata specific write up to follow. This is going on a 99 miata. Alot of threads end in you did it wrong because you didn't follow the official megasquirt manual so that's what I've been trying to use.

I tried following the trace as far as I could but there's to many components on the board. I'll remove those two FETs off the board tonight..

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Originally Posted by Matt Cramer View Post
To check for a short in the Megasquirt PCB, power up the Megasquirt on a Stimulator or on the car and check the following points for voltage with a multimeter.

You should find the same voltage as the battery voltage on the following points: S12, S12C, the center legs of Q9 and Q12, the left (non-banded) end of D3, the left leg of U5, and the left (banded) end of D9.

You should have 5 volts at the following points: S5, the two +5V holes in the proto area, the right (non-banded) end of D9, the right leg of U5, the left (banded) end of D19, and pins 1, 20, and 31 of the CPU.

Let me know where you find the correct voltages, and where you find the wrong ones
Thanks Matt, I will check this tonight when I'm home and report back.
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Old 06-17-2016, 12:03 PM   #6
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looking again, it's a bit outdated and needs updates on the flyback and Alternator.

i dont like the way he does the harness.

http://westfieldmx5.sgrkempen.be/ms3/99-05-ms3/
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Old 06-17-2016, 02:10 PM   #7
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Quote:
Originally Posted by Braineack View Post
looking again, it's a bit outdated and needs updates on the flyback and Alternator.

i dont like the way he does the harness.

99 ? 05 MS3 | Frank's Westfield MX5 99 ? 05 MS3 |
Thanks for the link.
Should I remove the components that are not shown on this diagram?

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MS3X help. No 12V at U5-80-capture_b73e9f9d3da9a0cdade65056aa05f26ff206ab80.jpg  
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Old 06-18-2016, 04:37 PM   #8
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WOW, I made a dumb mistake. I thought I triple checked but I had 12V going into pin27 instead of pin 28 #facpalm

Quote:
Originally Posted by Matt Cramer View Post
To check for a short in the Megasquirt PCB, power up the Megasquirt on a Stimulator or on the car and check the following points for voltage with a multimeter.

You should find the same voltage as the battery voltage on the following points: S12, S12C, the center legs of Q9 and Q12, the left (non-banded) end of D3, the left leg of U5, and the left (banded) end of D9.

You should have 5 volts at the following points: S5, the two +5V holes in the proto area, the right (non-banded) end of D9, the right leg of U5, the left (banded) end of D19, and pins 1, 20, and 31 of the CPU.

Let me know where you find the correct voltages, and where you find the wrong ones
All voltages check out now. Thank you Matt!

Do you recommend removing the not needed components for the miata? or just leave them on the board?

Quote:
Originally Posted by Braineack View Post
looking again, it's a bit outdated and needs updates on the flyback and Alternator.

i dont like the way he does the harness.

99 ? 05 MS3 | Frank's Westfield MX5 99 ? 05 MS3 |
Do you recommend removing the not needed components for the miata? or just leave them on the board?
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Old 06-18-2016, 05:08 PM   #9
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no leave them. no point on removing.

id just remove r13 and install a 1k between the left pin of r13 and right of r45 just below it. that will provide the 1K pull up for the crank input.

do the jumpers in that writeup.

then do the expander board flyback mod. s19 to d1 on the expander.

and then set the pots, and youre pretty much ready to rock and roll.
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Old 06-22-2016, 03:08 PM   #10
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Quote:
Originally Posted by Braineack View Post
no leave them. no point on removing.

id just remove r13 and install a 1k between the left pin of r13 and right of r45 just below it. that will provide the 1K pull up for the crank input.

do the jumpers in that writeup.

then do the expander board flyback mod. s19 to d1 on the expander.

and then set the pots, and youre pretty much ready to rock and roll.
I seem to have exceeded the max turns of the r56 pot. does any one know the equivalent resistance of that pot at Frank's recomended setting of

Quote:
Turn R56 about 12 turns to the fully anticlockwise position (you may or may not feel a “click”) and then turn R56 back about 10˝ turns clockwise
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Old 06-22-2016, 04:02 PM   #11
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I've never checked voltages. never really had an issue (only on early units where we weren't adjusting enough).
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Old 06-22-2016, 05:19 PM   #12
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Quote:
Originally Posted by Braineack View Post
I've never checked voltages. never really had an issue (only on early units where we weren't adjusting enough).
Problem is I must have broke the pot adjustment mechanism so I have no way to know what 10.5 turns clockwise is. I already pulled the pot off the board and was hoping that if someone had a MS3 board accessible on their bench if they could measure the resistance across pins 1 and 3 so I can just pop an equivalent resistor in it's place. If not I can just source a replacement part from digikey but the resistor way would be cheaper and faster.
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Old 06-22-2016, 08:59 PM   #13
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how does one do this? :P
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Old 06-23-2016, 02:12 AM   #14
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Quote:
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how does one do this? :P
JK I just ordered some more pot instead.
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Old 06-26-2016, 02:01 PM   #15
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What needs updating on the flybacks?
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Old 06-26-2016, 02:40 PM   #16
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Just need one wire from s19 to expander. See install docs.
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Old 07-01-2016, 09:39 PM   #17
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Quote:
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Just need one wire from s19 to expander. See install docs.
Sorry, where can I find S19? I found S12 from Frank's write up but I don't see S19. And D1 is the same D1 as this pic right?

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Old 07-01-2016, 10:33 PM   #18
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He means S12. Looks like you found the right page in the manual

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Old 07-13-2016, 05:08 PM   #19
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I'm finishing up the wiring harness and had a couple of questions.

for SPR input on the MS3 board I have
SPR1 = CANH
SPR2 = CANL
SPR3 = KNK (from knock module)
SPR4 = empty

On Frank's wiring diagram it has SPR4 going to the Alternator. I think he uses his stand alone alternator board. If I'm using the MS3X for alternator control what jumper should I have connected to SPR4?

Also this is probably a dumb question but... OEM narrowband goes into MS23. I should wire my Wideband analog signal to EGO2 on MS3X22 right and just select that channel in the config? I can just leave my narrowband sensor plugged in and ignore the signal.
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Old 07-13-2016, 05:29 PM   #20
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Alternator Control. Dead nailed. MS3 / MS3-Pro / MSPNP-Pro

From this thread it looks like I should have the Alternator pin (1O) go to Nitrous control 1 (24) and configure that as a PWM output.
And It looks like Alternator sense (1T) does not need to be connected?

Last edited by cyotani; 07-13-2016 at 08:46 PM.
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