820-00165 no power after water damage

[2informaticos]

You must check voltage when the fan spins...

 

[crea2k3]

PCH VCCSDIO BYPASS / PP3V3_S0 / C1208 - 3.2v pulse detected
PCH VCCSUSHDA BYPASS / PP1V5_S0SW_AUDIO_HDA / C1210 - 1.4v pulse detected
(PCH 3.3V GPIO/LPC PWR) / PP3V3_S0 / C1212 - 3.2v pulse detected
(PCH 3.3V THERMAL PWR) / P3V3_S0 / C1214 - 3.2v pulse detected
(PCH 1.05V ME CORE PWR) / PP1V05_S0 / C1250 - 1.04v pulse detected
(PCH 1.05V CORE PWR) / PP1V05_S0 / C1256 - 1.04v pulse detected
(PCH 1.05V PCIe/SATA/USB3 PWR) / PP1V05_S0SW_PCH_HSIO / C1261 - 1.04v pulse detected
(PCH 1.05V USB2 PWR)/ PP1V05_S0/ C1264 - 1.04v pulse detected
PP1V05_S0//(PCH 1.05V CLK PWR)/C1266 - 1.04v pulse detected
PP1V05_S0_PCH_VCCACLKPLL_R - 1.04v pulse detected
PP1V05_S0_PCH_VCC_ICC_R - 1.04v pulse detected
PP1V05_S0_PCH_VCCAPLL_OPI - 1.04v pulse detected

 

[2informaticos]

Be sure R7520/21/23 have correct values.
An overvoltage on 5V_S3 can trigger SMC protection.

 

[crea2k3]

R7523 was the one I replaced as water damaged, it’s within spec. R7520 has a very weird reading, so going to change it. R7521 also a bit off so will change that.

 

[crea2k3]

Ok I took them out of circuit and they test fine, so all three of those are good.

 

[2informaticos]

Possibly accumulated crap under CPU or/and SMC.
You can try to heat CPU, using quality flux.

Should be good to reball SMC also.

 

[crea2k3]

Thanks, is the CPU not underfilled on these, or is that just phones and ipads ?. Ill give the SMC a reball. What temp is safe for the CPU ?.

 

[crea2k3]

No sign of corrosion under the SMC, just pulled it and looks fine. Is it possible U7501 is damaged ?, as R7523 was damaged. Not sure if the voltages it produces are there?.

 

[crea2k3]

Reballed SMC, will has the same problem

 

[2informaticos]

No need to melt CPU balls.
No more than 180-200 degress, for 15-20s; sufficient to burn eventually accumulated crap.

You can try known good BIOS first, just in case.
Be sure U6101 has good solders and traces.

 

[crea2k3]

I have just noticed this next to the bios chip, I’m not sure if it is relevant as it doesn’t actually connect to any surface traces. The line is SPI_MOSI and shows OL at that test point.

 

[crea2k3]

In diode mode it shows 0.440 on that test point

 

[2informaticos]

You can't get OL there; in diode mode with red probe at ground.
That means internal trace for SPI_MOSI is broken.
Check continuity from R6112 to R6122/27; and the test pad, of course.
Run a wire where is needed...

 

[crea2k3]

Ignore that I had it in resistance mode, tests fine in diode mode. Have ordered a bios programmer to see if re flashing it helps,