820-3115-b

[WaShErE]

Hello every1,

I got a macbook for repair, i have green light + fin spin but no post + no backlight+ no video on screen.

I have vcore, c9796 was corroded and i changed it. Before me, also one person attempt to repair and i saw flux near pch and cpu area. On lvds cable dont have LCD_IG_PWR_E so i dont have any voltage on pin 2,3,4. U9000 i have input 3.3V but no output.

I dont have any light on USB when i plugged in it, no caps lock light either.

I tried PRAM reset nothing changed.

History is, one day owner opened it up and didnt see anything on screen so she hit on keyboard then it works a week. Then became like that, nothing on screen. Also went to service so classic answer "we need to change the motherboard" and cost a lot.

I'm very confused about diagnose it. Need help badly, thanks a lot.

[piernov]

Re: 820-3115-b

What's the exact voltage on CPU VCore?
Beeping with no RAM sticks? Tried one known good RAM stick in the slot furthest from keyboard?

[WaShErE]

Re: 820-3115-b

What's the exact voltage on CPU VCore?
Beeping with no RAM sticks? Tried one known good RAM stick in the slot furthest from keyboard?

Hello piernov,

PPVCORE_S0_CPU is 0.891V, it is beeping without sticks also i tried with single stick.

Board naked fan run first normal speed and getting faster in 5sec, i forgot to mention.

[WaShErE]

Re: 820-3115-b

There is no U3403-U3404-U3401-U7960 are they present? because when i checked the pdf not written nostuff.

[piernov]

Re: 820-3115-b

They are no stuff, they have BOM option DDRVREF_DAC.
Could be corrupt EFI.

[WaShErE]

Re: 820-3115-b

So i need to reflash bios? I didnt do it before, as i know i need to copy serial number from dump file to a new bios file right? And do you have a copy of that or where can i find macbook efi bioses for future purpose? Thanks a lot piernov. I will try on Tuesday i guess i just bought ch341a for program it.

[WaShErE]

Re: 820-3115-b

I just saw a youtube video, fan always high no video on screen then i checked the Q7812 pin3 i have 0V then i injected 3.3v there after that i checked voltages all now present but fan start with high now, not getting faster like before and still nothing on screen.

[piernov]

Re: 820-3115-b

It's normal to have 0V on Q7830 pin 3. If you inject 3.3V there you won't get PP3V3_S0, so no ALL_SYS_PWRGD, so no CPU VCore, so I'm confused when you say "voltages all now present" since it was the case at the beginning, but after injecting 3.3V on pin 3 of Q7830 it's not possible.
For BIOS/EFI requests there's a dedicated subforum.

[WaShErE]

Re: 820-3115-b

It's normal to have 0V on Q7830 pin 3. If you inject 3.3V there you won't get PP3V3_S0, so no ALL_SYS_PWRGD, so no CPU VCore, so I'm confused when you say "voltages all now present" since it was the case at the beginning, but after injecting 3.3V on pin 3 of Q7830 it's not possible.
For BIOS/EFI requests there's a dedicated subforum.

Morning, i was meaning im getting P3v3_S0_EN_L i have 3.3V but now i have 0.41v on P3v3_S0 which is not normal i guess? This is my first macbook experience.

On youtube video he doesnt have video on screen and fan ramp up, he jump a wire from R7382 pin 2 to Q7812 pin 3 because he doesnt have voltage on pin 3 and he get video on screen too. Thats why i tried it.