820-3208 TURNS ON BUT NOT STARTING, PPVCORE_S0_AXG 0V, U1800 Warm

[Bouba148]

Hi Team,
I have a 820-3208which had a liquid damage.
At the begining it had no sign of life then i replaced C5025 and passed it the Ultrasonic cleaner now the fan turns ON it, that turns ON (Fan spins) but doesn,t start:

after i've checked all the votages again i've noticed that PPVCORE_S0_AXG is at 0V:

PPBUS_G3H : 8,38
PP3V42_G3H :3,417

5V Rails:

PP5V_S5 : 5,126
PP5V_SUS : 5,126
PP5V_S3 :5,128
PP5V_S0 : 5,122

3.3V Rails:

PP3V3_S5 :3,331
PP3V3_S4 :3,330
PP3V3_SUS :3,331
PP3V3_S3 :3,325
PP3V3_S0 :3,325

PP1V8_S0: 1,786

PP1V5_S3: 1,355 MAYBE LOW?

PP1V5_S3RS0: 1,355 MAYBE LOW?

PP1V5_S0: 1,510

PPVTTDDR_S3: 0,678
PP0V75_S0_DDRVTT: 0,674
PPVCCSA_S0_CPU: 0,856
PP1V05_SUS: 1,042
PP1V05_S0: 1,072

PPVCORE_S0_CPU: 1,118
PPVCORE_S0_AXG: 0V
PP1V5_S3_CPU_VCCDQ: 1,355
PP1V05_S0_CPU_VCCPQE: 1,052
PP1V8_S0_CPU_VCCPLL_R: 1,787

Then I removed R7550, to notice that i have 2,8 Ohms between the ground and PPVCORE_S0_CPU_VCCAXG line ( Pin 2 of R7550), i have 0,833V at the pin 2 of L7550 without R7550 insteac of 1,05V.
i've also notice that U1800 is getting warm.
What should be the best way to troubleshoot that? should i remove all the capacitors on the on the CPU Decoupling page?

Thanks

 

[aprendiz]

Put back R7550, do a PRAM reset, PPVCORE_S0_CPU_VCCAXG will only come up with a display connected..

 

[Bouba148]

Hi Aprendiz, thanks for your reply,
i've tried a PRAM reset without sucess, so i took a look at U9000, this one doesn't receive the EN signal on pin 1 from U1800 SMC, 3,3V is pesent on pin 2 and 3 and R9014 is 99m8Ohms (1KOhm)
Has i precised it in the tillte, the SMC U1800 is getting war, that why i really suspect U1800.
Could you please confirm

Thanks

 

[aprendiz]

U1800 is not the SMC, is the PCH, and of course will get a little warm, what is the voltage on L7510?? Do you have the display connected???

 

[JohnB8812]

Your PPBUS Voltage is low at 8.38 volts. I suspect crap under the SMC or dead SMC

 

[Bouba148]

Sorry I don't know why i wrote smc , because i'm talking about U1800 ( PCH ) sorry.
Yes The screen is connected, regarding the voltage on L7510 i've mesured 1,125V instead of 1,25V.

What i did is that i've bypassed U9000 pin 2-3 and 4-5 to bring the 3,3V on L9004. But still PPVCORE_S0_CPU_VCCAXG stays to 0V.
I would supspect more the PCH U1800 than the SMC no?
If yes do you know the right reference of the PCH (U1800) , because i couldn't find the PCH on ebay with the ref in the pdf : " INTEL PANTHER POINT - MPCH U1800 1017P " or " QP8D-MM915462 "

thanks

 

[dukefawks]

Don't bypass things like that, that is a good way to completely fry the board.
Connect one of the speakers and check if there is a beep.

 

[Bouba148]

Hi Dukefawks, ok i'll remove the jumper i did.
The speakers are both connected and no chime and/or beep.

 

[dukefawks]

This could be anything. Corrosion under SMC? Where was the original corrosion?

 

[Bouba148]

Almost everywhere, it was a dark liquid like coca cola....because it was like caramel inside.

 

[dukefawks]

Corrosion under some chip. Could be SMC, could be PCH, could be RAM. You saw the original damage and you need to make an assessment as to which chips may have crud under them.

 

[Bouba148]

OK, so i think i'll re pass it in the UC if not OK, remove one by one smc, pch.
Which one should i remove first ? Smc or pch ? I would say pch as this one is getting hot.
But maybe before doing all that i'll try to get another screen to test it.
Can i try with a mbp 13 dispkay ?

 

[Bouba148]

Hi Dukfawks,
I've tried to plug 2 different display (mba 11, 2010 and mbp 13 retina 2012) and it's still the same no sound, no backlight, not booting so now the next step would be to inspect the smc, pch.
Which one first you'd recomand me ? Smc ?

 

[dukefawks]

Define "hot"? Can you keep your finger on it?

 

[Bouba148]

It's not burning if you keep your finger on it.
Just removed the smc and tried to put it back without reballing,(don't have the stencil), so now the fan spins then stops alternatively. I'll order a New reballed one and install it.

 

[dukefawks]

You cannot order a reballed SMC. They have firmware and cannot be exchanged between different board models. Get an identical donor board and reball that SMC.