macbook pro A2251, has 20v but very low amps, won't turn on

[tom_stringer98]

So i have this macbook, It won't turn on. it has the 12v rail present and is showing 20v when plugged into a charger, but there are shorts on pp3v3, specifically the caps i have circled in the photo of the schematics. they are both still short when the u7700 chip is removed. i'm a bit lost for what to do next. i've tried volt injection but i cannot get anything to show up. Anybody got any tips
Cheers

 

[Calenhad]

First of all, what you have circled are inductors. Not caps. As such they will measure close to a short if you try measuring resistance across them.

 

[tom_stringer98]

First of all, what you have circled are inductors. Not caps. As such they will measure close to a short if you try measuring resistance across them.

my bad they look similar. Is there anything else i can be checking at this point? as i have 20v coming in from all usbc controllers and 12v

 

[Calenhad]

All I can say is that the short you were measuring is most likely not a fault, so you need to start looking elsewhere.

I mean the caps are always suspects with power delivery faults (imho at least). Which are all the components starting with a C in your diagram (C7706, -07, -08, etc). But I am not competent enough to make a better suggestion as to where the actual fault might be.

 

[tom_stringer98]

All I can say is that the short you were measuring is most likely not a fault, so you need to start looking elsewhere.

I mean the caps are always suspects with power delivery faults (imho at least). Which are all the components starting with a C in your diagram (C7706, -07, -08, etc). But I am not competent enough to make a better suggestion as to where the actual fault might be.

Thanks for the reply, i just find it odd that it's taking 20v but won't turn on, i don't know where i should start to look in that case. i'm not the best a reading schematics as you can tell.

 

[kiddagoat]

Ummmmm if you don't know how to read a schematic or know what the symbols indicate.... you should just stop with that for the moment.

Have you tried different chargers? How does the battery look?

Do the fans attempt to spin up at all?

Are there any beeps or leds flashing?

 

[DirtyDingusMcgee]

+1 for charger and battery check

should be like 20.2v @ 4.3 amps .....1.8 way too low.

 

[tom_stringer98]

Ummmmm if you don't know how to read a schematic or know what the symbols indicate.... you should just stop with that for the moment.

Have you tried different chargers? How does the battery look?

Do the fans attempt to spin up at all?

Are there any beeps or leds flashing?

The battery is unplugged with that reading. But to my knowledge macbooks can turn on without the batterys plugged in? The battery does seem to be dead as well it gave me 1v last time i checked. No fan spin up, no beeps or leds flashing. Im guessing it's either ppbus g3 H or pp3v3?

 

[kiddagoat]

I would start with the USB - C Board.

MacBook Pro (A1989, A1990, A2141, A2159, A2251, A2289, A2338 Mid 2018-2022) USB-C Board

 

[tom_stringer98]

all 4 usb c ports are okay.. It's not only taking 5v into the board and ppbus isn't shorted on the fuse at f7000. nor can i find a short on pp3v3. i have check pretty much every cap at this point. i've injected 1v 2amp into ppbus from the fuse and nothing lights up either

 

[tom_stringer98]

I have just found that i cannot get anything on pp5v, is that correlated to anything? is there a chip that generates the 5v that can become faulty

 

[kiddagoat]

Is the charging port on the main motherboard or on a daughter board?

https://repair.wiki/w/MacBook_Pro_A2251

 

[tom_stringer98]

Is the charging port on the main motherboard or on a daughter board?

https://repair.wiki/w/MacBook_Pro_A2251

both ports on each side are connected via a flex that is then screwed into the laptop chassis

 

[kiddagoat]

I would check that link I posted. It may help.