820-3115 Does not recognize internal or external hard drive

[No-Clean]

Board had corrosion around the SMC top area both front and back of the board, after UC, clean BIOS and reballing SMC the problem persisted.

With nothing except the screen and power connected I get folder flashing.

With external drive connected via USB I get permanent white screen.

New RAM was also tested but same problem.

After checking J4501 I found PP5V_S3_IR_R was around 0.120 in diode mode and it was supposed to be 0.420 I found that Q7261 was slightly shorted, replaced that and diode reading is now normal and I get 5V on PP5V_S3_IR_R but still same problem.

U4510 diode reading in all pads is good but I replaced it anyways, same thing.

 

[2informaticos]

Tested both USB ports?
Can you confirm at least USB activity?
No external boot drive appears in boot menu?

Internal HDD problem may be caused by APFS not supported.

 

[No-Clean]

Yes I have USB activity in both ports, when starting up holding option key no drives appear in boot menu, I'm trying to start up from a non APFS formatted drive.

 

[2informaticos]

Is there EFI password present?

 

[No-Clean]

No, I did a clean known good BIOS with no EFI password.

 

[2informaticos]

Check if boots from DVD unit.

 

[No-Clean]

Nope, it doesn't I forgot to mentioned that I tried that also at the start of the repair.

 

[2informaticos]

Still get flashing folder?

 

[No-Clean]

Yes I get flashing folder, I hear the super drive trying to do something but all I get is flashing folder, I tried a few times with 10.6 CD.

Today while doing some more testing I got color lines flickering on screen, this is the 3rd time I see this, it goes away after I remove power and power on again.

 

[2informaticos]

There may be problems with CPU, or RAM.
Test with one PC3-10600 at a time (both slots).

 

[No-Clean]

Tried with one PC3-10600 at a time both ports same thing.

 

[2informaticos]

Bad CPU I supposse...