After some fairly extensive testing I'm fairly confident the CPU V3 Daughter board is shot on my MS3X. It's the one from DIY Autotune that you assemble yourself. I was hoping to find someone local I may be able to test the mainboard with something like a V1 CPU to see if it's at least working on a basic level. Powered on both inside and outside the car with 12V to pin 28 (DB37) and ground to all grounds gives me nothing. I can't communicate with it via RS232 or the USB serial on the MS3 daughter card. Voltage testing appears to give the correct readouts on the CPU socket of the V3 board but I can't get anything to detect on any computer (I've tried Mac, Windows and even linux via minicom to detect COM ports. I can't get anything to detect. I'm positive it's not a driver issue as I've tried about 6 different computers and had a sanity check with a few experienced people. What are my next steps? I don't want to buy a shiny new V3 CPU only to find out my board is a CPU killer or vise versa. I need someone who has the right means of testing. I've lurked for a few years but this is my first time reaching out in a thread. Thanks in advance.

 

bump

 

Well... for starters it would be good to have your location in your profile.

 

Ah, that would be good info wouldn't it? I'm from Dallas TX. Just updated it, thanks.

 

if the cpu board is getting power and you're not able to connect to USB, then you'll need to talk to Peter Florence about repairing the CPU board most likely.

Welcome to PFTuning.com

If you think it's NOT the white cpu board, you can probably fix it yourself with some google and brian.

 

I'm thinking Brian has been pretty busy with personal stuff lately. We've been going back and fourth a bit but I haven't gotten much out of him for a while. I just bit the bullet and bought a jimstim that should get here soon. I'm sure it'll get used more than once and worse come to worse I can sell it when I'm done with it. I'll report back if I get much further when I do some proper testing. Is there much testing I can do without the CPU in place on a jimstim? I'm just looking for SOME form of life from the thing so I can have somewhere to start.

 

sorry, i misspelled "brAIn"

and I meant yours, not The Brain.

 

You can do a basic power test. 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.

 

Found a difference in voltages on the 12v rail:
11.3v:
S12
Q9
Q12
D3

10.6v:
S12C
U5
D9

I found a thread where someone had a very similar issue here: http://www.msextra.com/forums/viewtopic.php?t=66196

I thought I had a bad D12/ D13 diode, but I've replaced D10, D11 D12, and D13 with no changes in voltage

Any ideas on what else I can test?

 

I found a difference in my 12v readings but my 5v is fine at all of those points mentioned.

 

pics of board please.

 

Yes, there is a small voltage drop through some of the diodes; those measurements are within spec. So at least the board is powering up OK.

 

https://drive.google.com/folderview?id=0B-G1NW6PZsTVU2hWcXRmb1dIb0E

 

Something worth mentioning, I get a solid fuel pump LED (FP) on the stim when powered on with the MS3 daughterboard. I only get a power LED when the board is powered without the CPU. Link to more pictures: https://drive.google.com/folderview?id=0B-G1NW6PZsTVU2hWcXRmb1dIb0E

 

why do you have the boot jumper installed?

 

I've tried with and without the boot jumper (specifically on the MS3 daughterboard)

 

tachselect in and out are jumpered on front of the board. (previous owner assembled it this way)



Here's some not-on-google-drive pics. I just went through and checked/ went over every solder joint and fixed any dodgy looking points. None of them were all that bad.

 

looks built correctly, so dunno.

 

So what next then? throw another MS3 daughterboard at it? I wish I could find another one just to plop in the board and see if it powers up so I know rather or not I need a new CPU. What other tests can I try? If I get voltages at all those points am I pretty much guaranteed to have a bootable daughterboard? I'm aware some people like Peter Florance can repair these daughterboard, I would just like to confirm it's the problem.

 

Any ideas what other voltage/ continuity tests I could try next? Is there a way I can see if the daughterboard is shorting somewhere or if a fuse was blown?