820-3437 no SSD in bios mode

Bouba148

New member
Hi Team,
This board came with a WD and not turning all at all, so I replaced many components ( I can provide the list if needed )

Now It doesn't boot on the OS from the ssd but boots from usb and once booted from usb it can see the ssd.
So the ssd is not detected in bios mode but detected in OS mode.

mesurements with ssd plugged in at U3740 are ok:

pin 1 = 3.42v
pin 2 = 1v
pin 3 = 3.3v
pin 4 = 3.42v
pin 6 = 3.24v
pin 7 = 0
pin 8 = 0

PP3V3_S0SW_SSD_FLT: 3.3V
SSD_PWR_EN: 3.250V

Checked all the PCIe data capacitors all are ok: resistance beween pin 1 and 2 around 2.5 MOhms for all 8 capacitors.

What are the signals to check in bios/spi mode? is it the smc that controls that ssd during the boot sequence or the SPI?
Maybe corroded or broken trace somewhere around that area.....

Thanks
 

Bouba148

New member
What is strange, is that it's not booting with some good external hdd or usb stick with os installer on them.
The screen turns light Grey with Grey apple logo : what does that mean that color code ?
You may right it's maybe an partition format issue.
 

Bouba148

New member
Hi Team, 2Informaticos

Finally I've found what was the "issue".
Maybe It is obvious for some of you guys but it was tricky to find; so I wanted to share.
In fact I've tried 2 different GOOD SSDs, not seen at the boot : folder with the ? mark, but if I boot on a installer from a regular usb stick, I could see the SSDs with disk utility then able to format in HFS and restore a SIERRA image on them with no problem, but still can't boot on them....HUMMM.....that made me crasy until I've tried a 3rd different SSD.
That last one was a Samsung and worked at the first time VS the 2 different others ( both Sandisk ).
Here is attached a picture of the 3 different SSDs ( 2 Sandisk and 1 Samsung ).

I Hope this will help some of you guys

You can mark this topic as SOLVED and close it

Thank you for your support

Click image for larger version  Name:	SSDs.jpg Views:	0 Size:	304.2 KB ID:	49118
 
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