820-0521 was dead with liquid damage, no post now

[kevinklinkmuller]

This one had a little damage with r7679,r7678,r7677,r7671. replaced them all, can't see liquid damage anywhere else but it did have a short with C7676, replaced that too.
Now the trackpad clicks so I guess it's kinda turning on but no post

 

[2informaticos]

Do you get voltage on the big coils?

Inspect audio board/flex for liquid signs.
Remove the small audio board and check both sides.

 

[kevinklinkmuller]

Actually i have audio board disconnected entirely just in case, is it required to post?

 

[kevinklinkmuller]

i get 0V on all the coils around the CPU
I get 12.3V on L7030
3.3 on l7690
2.6 on l7670

 

[2informaticos]

"2.6 on l7670"
Is that steady voltage?
Not good; check the correct ohm value for all R7671/7/8/9.
Be sure to have good traces.

Also check diode mode to ground at L7670.

 

[kevinklinkmuller]

Yep it's 2.6 on l7670 steady

Diode is 0.37

interesting, i mistakenly replaced r7671 with a 10k resistor instead of 10 ohm. i replaced it back to the correct one (they are all correct now) and now it doesnt show any sign of life, no track pad click either. I can see that p5g3s is only 90 ohms from ground. A little low isnt it?

 

[kevinklinkmuller]

diode mode on pp5v_g3s is 0.05. that's almost short right?

 

[2informaticos]

Check diode mode after 10-15s, once power removed.
You didn't have low value before.
Something happened when you've changed the resistors.
Be sure all have good continuity.

 

[kevinklinkmuller]

sorry i'm wrong, yes it's 0.35 diode now. My mistake
but l7670 is now 1.6V. what the hell. this thing is trolling me

 

[2informaticos]

Check all components and traces in the 5V_G3S power supply.
Pay atention to C7699 and R7664/5/6.

 

[kevinklinkmuller]

all checks out ok but it came back with the 0.05 diode on 5v rail. SO i injected 5V. I can see U810 heating up clearly. Took it off, normal diode readings. Then i replaced with another "GAY" chip from a different model donor. (i'm literally trying to find the donor i got it off and can't find it). The one that was originally on there is "GAY SJN" the one i replaced it with is GAY SJ5
It's the only chip i found that looks like is the right one. And sure enough it has normal diode reading with this but it still doesnt boot

also i think i solved the trackpad click mystery, there was a little tweezer nick in the flex, i sorted that and the click is back

 

[2informaticos]

Do you mean U8110?
Check if R8144/7 are both good now.

 

[kevinklinkmuller]

yes that's what i meant
they both measure good i think. R8147 measures 0 ohms and r8144 measures 4.5 ohms. I assume it's good? I see schematic lists as 2.2 ohms each

 

[2informaticos]

Can you complete DFU?

 

[kevinklinkmuller]

Wait, this is now turning on for no reason hahaha. But there's no backlight. just image

 

[kevinklinkmuller]

i also get keyboard backlight so i assume it isnt SMC lid right?

 

[kevinklinkmuller]

do you have any ideas what could be causing BL issues?

 

[2informaticos]

Did you try known good LCD assembly?
Do you get 5V_S0SW_LCD?

Check U8400 voltages; pins 5, 18, 11, 17.
Also check R8450-53 and their traces to J8500 and U8400.
Compare voltage and diode mode for SCL/SDA lines with good board; do the same for D8410.