820-4924 ppvcc_s0_cpu

[Melamanti]

Good Evening,

Customer brought in a 820-4924 with a green light and nothing going on other than that.
After some digging around i found out that it had no ppbus_g3h.
Restored that and now the machine wont do anything else.
Did some measuring around and i found that PPVCC_S0_CPU, is shorted.
Is there something i m missing or does that mean that the cpu is fried?
Machine has been ultrasoniced and of course messed around by previous stores.

 

[JohnB8812]

How do you know it's shorted? The CPU VCore line is a LOW voltage line it should have a low resistance/diode mode reading normally....why did it have no PPBUS was there a short corrosion etc? If shorted, what component?

 

[2informaticos]

"i found out that it had no ppbus_g3h.
Restored that"
What exactlly did you find there?

Do you get Magsafe light, any S5, or SUS voltage?

 

[Melamanti]

When i say it's shorted i mean that resistance to ground is 0?hm. Diode mode reading is 0.00v.
I restored ppbus_g3h by replacing q7310-7311-7320-7321. As I said before this board has been messed with already.
Using an original 60w magsafe 2 adapter i get a green light that turns amber as it should.
Using a dc power supply at 16.5V 4A , it shows a reading of 0.150A as soon as you plug the charger but it drops to 0.020 in a matter of seconds.
I suppose that something is preventing it from starting.
There is nothing getting hot.
There is pp5v_s5 but no pp3v_s5.
I have checked everything corresponding to that line and everything seems in place.
My assumption is that a power line beyond that, meaning an s4 or s3 line is having an issue and that's why it is not powering up.
I have also replaced u7501, and the smc from an excact same donor board.

 

[2informaticos]

"I restored ppbus_g3h by replacing q7310-7311-7320-7321"
Important thing, which you didn't consider to mention in first post.
Pretty sure you have dead CPU now; less than 1% chance to survive VCORE overvoltage.
Don't waste more time with this board...

 

[JohnB8812]

If Q7310 was shorted, this board is done. CPU got 12.6 volts RIP.