MSefi.com read only forum (Jan.15,2018)

Hello. I am new to megasquirt but when assembiling the MSII V3 i met a problem. I installed the powersupply and it was fine 5 volts everywhere i was ment to and then i went and followed the assembely instructions up to testing the clock was working and i checked the voltages again. They have gone down to 0.53 volts there is plenty of voltage going in 11.93v. I just cant seem to find the problem. Any help would be greatly appreciated. Thanks.

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 for the reply. All of the supply/12v are fine. The 5 volt however are
S5 0.68Volts
The two 5Volt supplys on the proto area read 0.68 volts
The non-banded side of d9 read 5.1 volts
The Right leg U9 read 5.1 Volts
And pins 1/20/31 read 0.68 Volts.
Thanks again for your help.

Try desoldering the D19 diode and repeating the measurements. D19 can short out and pull the 5 volt plane to ground.

I have desoldered it and the voltages seem to be fine. Will it just be a case of replacing it? Thanks

tomsmooth wrote:I have desoldered it and the voltages seem to be fine. Will it just be a case of replacing it? Thanks

Correct, sounds like yours burned out.