820-00138 PP5V_s0 shorted to ground. RIP CPU?

Alan.L

Member
customer plugged usb hub and apparently has killed the board.

i found out PP5v_s0 is shorted, i then removed Q8060, U4600 and can confirmed PP5V_S0 is definitely shorted.

i then injected 5v to PP5v_s0 but nothing gets warm. also my psu has limited 5v on PP5v_s0 to 1.7v :(

i think it might have killed the CPU via U7330/u7310

any suggestion??
 

2informaticos

Administrator
Staff member
If there is very low value to ground, start injecting with 1V.
Monitor the current and go up, maintaining ampers bellow power limit; set its limits to max (5-10A).
If you start with 5V, power supply can get blocked reaching ampers limit and will not inject anything...
 

Alan.L

Member
I did start from 1v. but with 2.4v - 4v its drawing 1.7v @ 5.76amp and nothing get warm.


gonna put this board back to the bottom of the pile. i'll get 10AMP power supply someday.
 
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2informaticos

Administrator
Staff member
If you have 5A bench power supply indicating 5.76A, is already blocked; it doesn't inject anything in that moment, nor even 1.7V.
Maintain current under 5A (at limit) and check voltage on the board with DMM.
1.4V/5A (as example) means 7W which should heat something.
Unless you lose power on the leads connected between power supply and MLB; use strong wires.

Also remove any heatsink from the board.
CPU will not heat so easy, as it has many contacts with the board...
 

Alan.L

Member
Yes, when i inject any voltage then check with a multimeter on the board, it only taking 0.3v. I?ll try again in a bit. Thank you :)
 

Alan.L

Member
is it wise to remove the U7330, U7320 and U7310, so the bench power supply can concentrate the board without CPU?

so far i've removed U7600, R7201 (power to cam), R19920 (SPI stuff) only left to remove are the 3 CPU PHASES.

after i removed the three PHASES, can i try inject more than 5v to PP5v_s0?

i think the short is inside the board
 
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Alan.L

Member
it was the cpu phases, not sure which one tho.

Got a Fan spin BABY!!!!

i dont want put the new replacement in, just want to enjoy watching the fan spinning...





#edit

i've found you SUCKER

 
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Alan.L

Member
mmm, the board is working now after replaced the two phases with FDMF6708N.

but no backlight. yes got an image. 0v on pin1. fuse is good.
probably a dead U7701 driver...
need to check SMC_Lid first...

got 2 known working MacBook pro 15" display assembly here,


do you know if i can use a 13" 2015 screen for testing?
15" is too big to work with. like 11" Air screen works on 13" logic board vice versa.
 
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Alan.L

Member
boot to apple logo, a quarter of the way then laptop reboot.

i used FDMF6708 on U7330, U7320 and left the U7310 with original FDMF6808. can this be a problem?

or can it be something else, replace everything that use PP5V??
 
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Alan.L

Member
mmm, can boot to OSX fine from the internal SSD but not an external USB boot drive. the original problem was a USB hub killed the logic board which makes perfect sense.
however USB port does work, i can browse a USB drive perfectly fine.

starting to hate this board.
 
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