820-00923 no screen no touchbar

[Nick]

got a pre worked on 820-00923, they replaced c7053 c7055 r8442 and edp connector. fan spin and all. no idea why they replaced all of that, they usc it so i have no clue remaining. i saw more oxidation on u8500 and u8501, repalced those to be sure but still no panel_3v3_en and panel p5v_en

 

[JohnB8812]

Any sign of corrosion near the CPU on the front side? If so, this is probably dead. Apple made a stupid design on the LCD connector and put the backlight line next to a CPU data line.

 

[Nick]

no, damage was only on the back/keyboard side. although this was uscd before

 

[JohnB8812]

Look very closely near the caps and fets above the CPU for any signs of previous liquid damage. If nothing, then this won't be super fun is CPU VCore present?

 

[Nick]

i checkd and it seems clean. customer said it worked on external screen. i got image on external once. now nope. cpu is getting warm (not hot) i get 1.1 on l7270, l8050 and such, but i have no voltage on l7220 l7210 l7410 l 7420 l7430

they are all from 3 to 7 ohm to ground

 

[2informaticos]

If you got external image this can point to internal video out issue on CPU.
Usually caused by overvoltage from backlight to CPU video outputs after liquid damage.
Strange that you got external one time only.
You can now put good flux and reflow CPU area.
You may have luck and is only crap which blocks some data bus...

 

[Nick]

i did not know that i could have a working cpu with dead outputs. interesting. i have replaced cpus before (in other machines), so in case i can replace this one too. Is it possible to source good ones?

 

[JohnB8812]

If you get external video, but no internal, you likely have a dead MUX. If you get neither, this is probably a dead CPU.