Help with MS...
 

Alright, here's the deal. Due to a little to much beer during my MS install I managed to connect the MS grounds to a powered wire in the Miata harness... now the MS will not power on. No signs of anything damaged, neither visual nor by sniffing. It did power on prior to the mishap, I was swapping wires to address a connectivity problem and was hoping for a better ground.

I'm looking for someone that is trustworthy and knowledgeable that is willing to take a look at it for modest compensation... or someone willing to trade as-is for an FMU with a few disks.

This was a pre-assembled unit purchased from Protocar. But they don't seem to like answering emails...

Or for that matter I will trade for a SAFC II or similar...

what error message to do you get when trying to connect to megatune?

you most likely fried the CPU.

throwing $20 to diyautotune.com should fix your problem for a new MSI CPU.

No error codes. Prior to drunking up the wiring I would get disconnected at random. Now I don't get a power light from the MS...

first, i'd soberly verify the wires are correct. and if so i'd consider a new cpu.

+1 on a new chip also inspect the baord for burnage

"4. Next, you are going to install the components that make up the power supply, and then verify operation. The first part to install is the 'Perry' Metal Oxide Varistor MOV1 {P7315-ND}. This is a large flat disc, about an inch (~25mm) in diameter. It is soldered near the DB37 connector, and does not have a polarity, it can go either way around. This part protects the MegaSquirt from surges on the 12 volt line. "

Yeah, uh.... I was wrong.

Yeah, I've done that, times three at this point.

No signs of burning that I can see...

I'll look into the power side of the schematics next....

Did you look at both sides of the board? How about where the harness is connected?

it's incredibly easy to fry the cpu. i did it by handling my MS while it was powered up with the stim and completely opened up. My fingers must have touched something it didn't like.

Both sides of the board, yes. I'll go over the harness.

Would a fried CPU prevent the unit from powering on.

No, http://www.megamanual.com/ms2/V3assemble.htm

Step 23 tells you how to check the power supply circuit. this will confirm that section isn't fried. Step 26 will tell you how to check the serial comms.

That's as much as you can test sans processor afaik.

Are you still getting 12V across the wires going to the MS?

Thanks for the link, I will check these things out as soon as I un-borrow my multimeter.

This should be the next thing to check... may have just popped a fuse outside the MS unit.

Hmm. I'll give that a look... I tried checking my timing after all of this but jumping the terminals didn't seem to have an affect. Or at least the CEL doesn't come on...

Measure for continuity across D19 (5.6V Zener). If it reads as shorted in both directions, remove it and apply power. Replace it if you want to maintain short circuit protection.

I accidentally shorted, IIRC, 12VDC to ground on the MS and popped that diode. It's there for short circuit protection anyway.

There is also the D12 diode, which does much the same thing for the 12 volt side that D19 does for the 5 volt side.

D19
.709
.407

D12
.638
Infinite

I take it that that means D19 is bad?