Macbook Pro 13" A1708 820-00875 PP3V3_S5 shorted

ielectron

Member
Hi,
I got for repair MacBook Pro 13" 820- 00875-A after liquid damage.
I check all rails and PP3V3_S5 is shorted
PPBUS_G3H 13.10V
SN650839 have some voltages coming out:
PP5V_LDo5V
PP3v3_LDO3V
PPBUS_PMIC
PP1V25_VREF
all those are present
voltage on C7960 PPBUS_G3H_CPU 13.10V
SMC have communication with charger as its changing from 5V to 20V after plug it in.
I do some checks but not really able to find what causing short, after insert 3V into this rail nothing really gets hot on board only CPU a bit. Mainboard takes 4,5A on this rail at the moment.
I have removed U7650 and U8205 and to check if this will cause short but it is not.
Any more ideas ?
Thanks
 

2informaticos

Administrator
Staff member
Start injecting with 1V and go up; no more than 3.7V and less than Amp limit of your becnh power supply.
BTW, the exact value of the short?
Of course, remove heatsink and tocuh CPU die directly with the finger.
 

ielectron

Member
Hi, i tested board with removed heatsink previously and now again and one side of cpu gets hot, exact value 1.1Ohm on the PP3V3_S5 rail. Also I have second working board to compare resistance and on L8060 its only 1.2ohm same on L7900. On working board resistance is around 56ohm on this two coils.
 

2informaticos

Administrator
Staff member
"resistance and on L8060 its only 1.2ohm same on L7900"
Both go to PCH; clearly marked on L7900 side.
So you have short not only on 3V3_S5; which also goes to PCH.
When you find short on 2-3 power supply, the common load is first suspect PCH in this case.

"one side of cpu gets hot"
I bet for PCH area...
 

2informaticos

Administrator
Staff member
If is two dies package, smaller one is PCH.

For one big die only, CPU area is close to VCORE coils.
PCH is on the other side of die; you can see RTC components placed near it.
 

ielectron

Member
With all measurements and checking looks like CPU/PCH is gone... Have you ever try to replace it ? I have replace many GPU PCH and older CPU successfully but never try to replace any of this newest Intel. They are expensive so I wondering is it even worth to trying. Thanks
 
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