Troubleshooting CPU circuit on MS3 after ground failure

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Tachyon
MS/Extra Newbie
Posts: 13
Joined: Mon Dec 11, 2006 3:36 pm

Troubleshooting CPU circuit on MS3 after ground failure

Post by Tachyon »

Hi all,

We've been running a pre-build SMD MS3x from DIY in our Audi stage rally car for the past 2 years and have really enjoyed the product.

Unfortunately at our last event, during a specifically rough stage, we had the ground wires that MS uses become detached and the ECU immediately stopped working. After some basic troubleshooting I can get the power and communication circuit to work, as long as I pull the MS3 daughter board out, but as soon as I plug the board back in I cannot connect over a hyperterm. I initially thought the CPU had bit the dust, so I ordered a new MS3 daughter board. Unfortunately after plugging the new board in, the MS unit shows the same symptoms as the old CPU - no communication circuit. I am hoping someone who has familiarity with the physical board layout could help get me started with what components I could have fried when the ground failed?

Thanks to all, I really appreciate the support from this board.

-Paul
Car 823 - Audi Coupe Quattro - MS3x - Rally America
Car 43 - 2003 Hyundai Tiburon GT - MS2 extra - World Racing League
1991 Eagle Talon - MS1 extra HR - 548 AWHP street car
Matt Cramer
Super MS/Extra'er
Posts: 17499
Joined: Thu Apr 16, 2009 8:08 pm

Re: Troubleshooting CPU circuit on MS3 after ground failure

Post by Matt Cramer »

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.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
Tachyon
MS/Extra Newbie
Posts: 13
Joined: Mon Dec 11, 2006 3:36 pm

Re: Troubleshooting CPU circuit on MS3 after ground failure

Post by Tachyon »

Thanks for your response, Matt.

I followed your instructions and here's what I found:

JimStim Voltage: 11.35

S12: 11.35v
S12c: 10.62v
Q9 - Center Leg: 11.35v
Q12 - Center Leg: 11.35v
D3 - non banded: 11.35v
U5 - left leg: 10.62v
D9 - banded: 10.62v

S5: 5.04v
5v1: 5.04v
5v2: 5.04v
D9 - non banded: 5.04v
U5 - banded: 5.04v
D19 - banded: 5.04v Note, on my SMD board the banded side was on the right.
Pins 1,20,31 and their grounds check out, 5.04v

-Paul
Car 823 - Audi Coupe Quattro - MS3x - Rally America
Car 43 - 2003 Hyundai Tiburon GT - MS2 extra - World Racing League
1991 Eagle Talon - MS1 extra HR - 548 AWHP street car
Matt Cramer
Super MS/Extra'er
Posts: 17499
Joined: Thu Apr 16, 2009 8:08 pm

Re: Troubleshooting CPU circuit on MS3 after ground failure

Post by Matt Cramer »

OK. When doing the communications check, are you using the RS232 port or the USB?
Matt Cramer -1966 Dodge Dart slant six running on MS3X
Tachyon
MS/Extra Newbie
Posts: 13
Joined: Mon Dec 11, 2006 3:36 pm

Re: Troubleshooting CPU circuit on MS3 after ground failure

Post by Tachyon »

I am using the RS232 port. To restate for clarity, if I jumper pins 12 and 13, I get echo back on my testing computer both through a MS suggested serial-to-usb and the MS suggested serial to blue tooth transmitter. But if the MS3 daughterboard is plugged into the socket, the exact same replicated test fails.
Car 823 - Audi Coupe Quattro - MS3x - Rally America
Car 43 - 2003 Hyundai Tiburon GT - MS2 extra - World Racing League
1991 Eagle Talon - MS1 extra HR - 548 AWHP street car
slow_hemi6
Super MS/Extra'er
Posts: 4122
Joined: Fri May 07, 2004 3:33 am
Location: Australia

Re: Troubleshooting CPU circuit on MS3 after ground failure

Post by slow_hemi6 »

Have you tried the port check utility? what about reloading firmware with the boot jumper?
Find the Manuals up top under Quick links: Manuals. :RTFM:
Cheers Luke
Tachyon
MS/Extra Newbie
Posts: 13
Joined: Mon Dec 11, 2006 3:36 pm

Re: Troubleshooting CPU circuit on MS3 after ground failure

Post by Tachyon »

slow_hemi6 wrote:Have you tried the port check utility? what about reloading firmware with the boot jumper?
Well I know the port on my laptop works because I am able to make a connection that echos back commands to MS so long as the CPU is not installed. I tried a brand new CPU which will have the code flashed on to it, when I try nothing happens because it cannot make a connection due to aforementioned issue 1.

Fun stuff :D
Car 823 - Audi Coupe Quattro - MS3x - Rally America
Car 43 - 2003 Hyundai Tiburon GT - MS2 extra - World Racing League
1991 Eagle Talon - MS1 extra HR - 548 AWHP street car
Matt Cramer
Super MS/Extra'er
Posts: 17499
Joined: Thu Apr 16, 2009 8:08 pm

Re: Troubleshooting CPU circuit on MS3 after ground failure

Post by Matt Cramer »

New CPUs ship without firmware.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
Tachyon
MS/Extra Newbie
Posts: 13
Joined: Mon Dec 11, 2006 3:36 pm

Re: Troubleshooting CPU circuit on MS3 after ground failure

Post by Tachyon »

Good to know, Matt. It's not connecting at any rate. Gets stuck at:

TX:51
Waiting...
Waiting...
Sent Q and got 0 bytes back.
TX: 0d

Matt do you offer repair service for 3.57 PCBs?
Car 823 - Audi Coupe Quattro - MS3x - Rally America
Car 43 - 2003 Hyundai Tiburon GT - MS2 extra - World Racing League
1991 Eagle Talon - MS1 extra HR - 548 AWHP street car
Matt Cramer
Super MS/Extra'er
Posts: 17499
Joined: Thu Apr 16, 2009 8:08 pm

Re: Troubleshooting CPU circuit on MS3 after ground failure

Post by Matt Cramer »

We do if we originally built it. Email us directly at websales@diyautotune.com.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
slow_hemi6
Super MS/Extra'er
Posts: 4122
Joined: Fri May 07, 2004 3:33 am
Location: Australia

Re: Troubleshooting CPU circuit on MS3 after ground failure

Post by slow_hemi6 »

Tachyon wrote:
slow_hemi6 wrote:Have you tried the port check utility? what about reloading firmware with the boot jumper?
Well I know the port on my laptop works because I am able to make a connection that echos back commands to MS so long as the CPU is not installed. I tried a brand new CPU which will have the code flashed on to it, when I try nothing happens because it cannot make a connection due to aforementioned issue 1.

Fun stuff :D
Port check utility is a program you download from DIY. It does more than tell you if you have a working port or not.
Find the Manuals up top under Quick links: Manuals. :RTFM:
Cheers Luke
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