820-4924 not detecting SSD (liquid damage)

[chicocomputerclinic]

Hi guys!

Long time lurker

Anyways, I had a 820-4924 come in with liquid damage. Most of the damage looked like it was around thunderbolt related stuff. Went through the ultrasonic, fired right up... no SSD detected. Tested the SSD externally on my iMac and it works fine.

Checked U3740
Pin 1: 3.4V
Pin 2: 0.1v
Pin 3: 0.1v
Pin 4: 3.3v
Pin 5: Ground
Pin 6: 0.1v
Pin 7: 0v
Pin 8: 0v

PP3V3_S0SW_SSD_FLT I get 3.3v


Things I replaced already... I started getting desperate.
U3740
R3741
R3742
C3740
U3711
U3710
U8070

Both SSD_RESET_L and SSD_PWR_EN that are low appear to come from the CPU... which kind of worries me

I'm not in front of the board anymore for the night but I will take any advice on where to go tomorrow.

 

[2informaticos]

You may have corroded/broken traces around U3740.
If PP3V3_S0SW_SSD is present, you MUST have aprox 1V at pin 2/U3740.
U3740 can also be bad, as you cannot have 0V at pins 6, 7, 8 at the same time; look at internal diagram.

 

[chicocomputerclinic]

You may have corroded/broken traces around U3740.
If PP3V3_S0SW_SSD is present, you MUST have aprox 1V at pin 2/U3740.
U3740 can also be bad, as you cannot have 0V at pins 6, 7, 8 at the same time; look at internal diagram.

R3741 Pin 1 is 3.3v, pin 2 is 0.1v... even with U3740 removed. R3741 and R3742 are measuring ok. I see R3740 on the schematic and it doesn't say NOSTUFF but I don't have it on my board.. it wasn't there in my before photos. I don't have another one of these boards to see if that part should be there or not... but it's the same thing on the 820-3536 board, missing but on the schematic.

 

[2informaticos]

"R3741 Pin 1 is 3.3v, pin 2 is 0.1v... even with U3740 removed. R3741 and R3742 are measuring ok"
A simple calculation will show you aprox 1V as result.
Also good U3740 cannot drop that voltage.
So clean the board, change the resistors.

"I see R3740 on the schematic and it doesn't say NOSTUFF but I don't have it on my board"
As per schematic, there are some components marked "SSD_CLK_REQ : UNI/BI".
I hope you understand what that means.

BTW, do NOT quote an entire post from few cm above...

 

[chicocomputerclinic]

Ok so checked R3741 and R3742 again and the values just kept bouncing up and down super low sometimes way too high, but mostly low. I removed R5580 and then the values jumped to what you would expect and stayed there. I left for the night but I'll have to look into this Tomorrow...