Macbook Pro - Water Damage - 820-4924 | A1502 EMC 2835

[LCDR2]

Hello All,

First time poster and first board repair (Beyond removing surface corrosion!) so be kind

I have a client board brought in for water damage.

He's had it in the cupboard for about 6 months because Apple said it's stuffed.

There was some minor corrosion around the U1845 chip which seems to be part of the CPU - JTAG isolation circuit so I don't know how vital that is. `

--
We get

Green light on charger
27m amp draw (possibly 25 I don't know how accurate my supply is)

I measured the following, (I have included what I was near in case I'm looking in the wrong place)

Rail	Result	Enable?	Near Chip
PPV5_S5	0.5 V	1mv	U8100
PPV5_S4 (FETR)	2.8mv	0.4mv	U8100
PPV5_S3	3.29v
PPV5_S0	17mv	0.5mv	U8030
PPBUS_G3HOT	I assume works ""

I must admit I lashed out on all the "toys" as part of a government stimulus - pre EOFY binge so I have the Union Repair thermal camera (already helped me fix an SSD!) and I can see no "hot spots"

I have also Ultrasonic cleaned the board, however I do have photos of the original areas of damage.



General advice as to how to go about diagnosis as well as specific criticism on this repair is welcome.

Kind regards,

James

 

[2informaticos]

First of all, welcome to the forum!

If missing S5 voltages, no reason to check for S0, nor S3 ones.
Try to catch the logic of power on sequence; G3H -> S5 -> S3 -> S0.

Let the bench power supply apart and use original 60/85W Magsafe 2 charger.
Try to turn the board on with both charger and battery connected.
On charger only, try to start in SMC bypass mode also.

Post PM_BATLOW_L, SMC_PM_G2_EN and exact PPBUS_G3H voltage (F7140).

 

[LCDR2]

Hello 2 informaticos,

Thank you for the quick reply. Sorry it took so long to get back to you.

Using genuine charger.

Tried SMC Bypass using https://support.apple.com/en-us/HT201295. No sign of life (fan spin, etc)

Other measurements as follows with and without battery.

	W bat	Wo Bat
PM BAT LOW	0.551v	19mv
SMC_	1.058 / 1.057	1.060
PPBUS	13v	12.56v

 

[2informaticos]

Both SMC_G2_EN and PM_BATLOW_L are bad.
Looks like SMC issue; reball it and comment.

Battery looks bad also...

 

[LCDR2]

Thanks will do.
I will need to order / obtain a stencil, so it will be a while till my next post on this issue.

Thank you for the advice so far. Hopefully my replies are clear and complete enough to make your jobs easy.

I have a macbook air which came in today. I will post pictures of that tomorrow. it's a doozy!

James

 

[LCDR2]

Hi,

Do you have any advice on how to remove the SMC from the board.

I have the Hakko hot air gun FR 810B and flux (maybe not the same as you guys) but I can't get the chip to budge.

When people do it on youtube it literally seems to take 2 - 3 minutes max.

Is there a certain kind of flux that will help move the heat to the right places?

I never get "dancing chips" like Louis in his video's

Cheers

James

 

[2informaticos]

You must practice on scrap boards.
I have the same hot air station, but you must adjust settings accordingly.
I use 400-450 for temp and 2-3 for air.
The flux quality is not very important when remove components.

Remove heatsink, this make the job easy.

 

[LCDR2]

Hi

No heat sync attached. I am using the standard nozzle that it came with, maybe that's too narrow? I can't think of any more variables!

I have tried with the board sitting on the desk on a heat mat, and up in the board holder.

Nothing else is connected to the board (heatsync etc).

 

[2informaticos]

I use the biggest nozzle, 8mm.
You must approach up to 5-10mm and apply heat in circles.
First heat a larger area around SMC.
A small preheater, like Mlink 853A will help a lot.

 

[LCDR2]

nozel did the trick off in 2 mins.. LOL -

Thanks!

I'll reball and let you know how I went.