820-01987-A

[Anterweb]

Had a guy call me today that said his macbook had stopped turning on and he had taken it to Apple to repair, They told him originally that it was a faulty logic board and quoted over £1000 to repair. Then whilst thet still had the mac they sent him this,.


I agreed to take a look for him.

The mac wont turn on at all no fan spin, nothing in SMC bypass no real signs of life but I do get trackpad click when power connected,

The usb Amp meter immediately draws 20v and shows enough Amps to presume its charging the battery on both ports. so I cant see any fault at all with the USB ports they look immaculate and both take 20v and charge the battery,

I tried DFU revive but got the following errors half way through.


I Have never worked on one of these before so any advice on where to start much appreciated.

 

[2informaticos]

Check for short on all big coils of the board.
Don't forget L9080.

 

[Anterweb]

Before even removing the board,
( Obvs no bat or power connected )
I get continuity beep to ground on both sides of

L7270
L7220
L7410
L7420

L9080 dosent short to ground,

 

[2informaticos]

Continuity beep is not equal short!
And not always only short is bad; lower value than normal may not beep, but may be bad.

CPU coils have low resistance to ground as normal.
You must check in ohm scale and compare with good board.

 

[Anterweb]

Kinda knew this but just dont have another one of these boards to use as a comparison, Is there another method?

Does the Paul Daniels - flexbv contain this information?

 

[Anterweb]

anything else I can do with this dude?

 

[2informaticos]

Any pulse on SSD and G3S voltages?

 

[Anterweb]

checking for pulse on ssd I checked

C9074 -12.57v solid

L9030 - 1.80v solid
L9020 -.908v solid
L9021 -.908v solid
L9080 -.2.51v solid
L9080 - 2.51v Solid
Not sure what else to check here?

ALL GS3 voltages are present and correct and solid

Measured with just charger no battery connected,.

 

[2informaticos]

Check for pulse on other coils; like RAM, PCH, CPU...

 

[Anterweb]

Going over all the coils I can find.

Nothing pulses at all

L8410 - Starts at 30,0mV and slowly drops
L8456 -5.1v solid
L7220 - 0v
L7270 - 0v
L8102 -0v
L8100 -0v

L7030 -9.80v solid
L7690 -3.23v solid
L7670 - 5.08v solid

I'm stumped.

 

[2informaticos]

You should try DFU restore.
This will erase SSD...

 

[Anterweb]

Tried a few times,. Just get this each time

 

[2informaticos]

Check for short on output power rails in page 74; like 1V2_S3, etc...
If all good, then reflash U4770 and try again DFU restore.

 

[Anterweb]

Will check output rails shortly,

reflash U4770 , This is a new one on me, presume this cant be done with medussa,?
I have a ch341A does this do the correct voltage for this chip, and realistically how much of a ball ache is and what kind of success does it have? Im more tempted to hand this back as a no fix?>

 

[2informaticos]

That is 1.8V SPI chip; use correct addapter for it.
Harald sells an adapter board which can be used.