820-3462-A A1425 won't recognise SSD

Melvinzill

Member
Hi, have this really tough A1425 2012 retina board. It won't recognise a SSD even with a know good drive and known good caddy. All power lines at J4500 are present as expected. How do I properly check the data lines?
 

2informaticos

Administrator
Staff member
Check all resistors and capacitors from page 37; as their traces too.
You should also try known good flex.
Chinese new can be crappy...
 

Melvinzill

Member
By Caddy I meant the Plastic Caddy with its flex. Used one streikt from a working machine so that can’t be at fault.

I replaced R4506,4507,4508 and 4510 with ones from a donor as well as C4522 and C4525. I haven‘t replaced C4518 and C4517 yet as they are so close to the PCH.

In regards to the traces, I traced all 4 SATA signals to their resistors and then capacitors but its not possible to trace them beyond that so a bad PCH or not properly soldered PCH could still in theory be a unlikely cause for this, can’t it?

What else to check next?
 

2informaticos

Administrator
Staff member
"I replaced R4506,4507,4508 and 4510 with ones from a donor "
Was any bad?
Did you check if new ones have correct values?

Any history available?
Are you sure BIOS supports APFS (if is the case)?
Boot USB macOS and look in Disk Utility...
 

Melvinzill

Member
The drive isn’t APFS as it’s running Mavericks. None of the resistors were physically damaged or gave non nominal readings. same for the new ones. Don’t have any history on the machine. I did boot a copy of Catalina from usb and it didn’t recognize the disk.
 

Melvinzill

Member
Update: Someone told me it could in theory be a problem with the bios. I changed the SPI flash with one from my donor but that didn’t change anything
 

2informaticos

Administrator
Staff member
Check diode mode to ground on data lines and compare with good board.
Check on both caps sides, where is the case...
Do it w/ and w/o SSD connected.
 

Melvinzill

Member
Here are some readings without the drive plugged in:

SATA_SSDRHDD_R2D_N - OL
SATA_SSDRHDD_RC_N - OL
SATA_HDD_R2D_C_N - .330
SATA_SSDRHDD_D2R_N - OL
SATA_SSDRHDD_D2R_RC_N - OL
SATA_HDD_D2R_N - .360
SATA_HDD_D2R_P - .361
SATA_SSDRHDD_R2D_P - OL
SATA_SSDRHDD_R2D_RC_P - OL
SATA_HDD_R2D_C_P - .333
SATA_SSDRHDD_D2R_P - OL
SATA_SSDRHDD_D2R_RC_P - OL


The only changes I found with a plugged in SSD:
SATA_HDD_R2D_C_P - .333 --> .332
SATA_HDD_R2D_C_N - .330 ---> .329
SATA_HDD_D2R_N - .360 --> .357

Seem to me like more of the tolerances of my meter...

Sadly have no know good board to compare with
 

2informaticos

Administrator
Staff member
I don't have any board to compare, sorry.
I don't see any strange value, but I'm not sure what should get on all data lines...
If there is a serie coil, check if is close to 0 ohm (internal resistance); even on power rails.
 
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Melvinzill

Member
Quick Question: Noticed there are 2 lines going to the SMC. Are they required or are they just used for monitoring or something?
 

2informaticos

Administrator
Staff member
Is true, NO STUFF; just saw it now.

You can suspect PVH issue now.
But should be good to compare all lines against working board.
 
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