820-00138 A1398 Macbook Pro 2015 - No green light on charger

[SamMac]

I've got an issue with this logic board and the lack of a boardview makes it harder to diagnose. The ISL chip (U7100) gets warm I've got good readings at both PP3V42_G3H and PPBUS_G3H. Some concerns I have is I have no readings for SMC_BC_ACOK_VCC and my reading for SMC_BC_ACOK for both pin 1/2 is showing around 1.8V. Also my ADAPTER_SENSE voltage is showing at 0.7V. My U700 only gives voltage at adapter_sense and U7001 at pin 1/2 and pin 5 (PP3V42_G3H).

I've looked at every possible components linked to these for shorts but to no avail. I was hoping if someone can shine some light to my situation or give me some general guidance in how to diagnose macbooks.

Also I am using the 85W charger for this board so my readings should be accurate.

Thank you,
Sam

 

[dukefawks]

SMC_BC_ACOK should be 3.4V. Check resistance to GND on this line and check the pull up R5087.

 

[SamMac]

Yeah that's what I thought.
Resistance at pin 1 and 2 shows 429 (in diode mode). Couldn't find R5087 but found R5187 which gives 680 (in diode mode)

If I were to measure it in an actual setting then which one? (200, 2K, 20K, 200K etc)

 

[smiba]

Usually you can start at 200 and move up until it starts showing you a result.

In this case R5187 is supposed to be around 470KOhm, so you should select 2M.

 

[dukefawks]

Need resistance to GND and not diode mode.

 

[SamMac]

For R5187 i get 0.47 - 0.478 MOhms.

(I can't find anything either in the schematics or boardview on R5087.)

 

[dukefawks]

Still waiting for SMC_BC_ACOK resistance to GND....

 

[SamMac]

Been trying to get an actual reading at SMC_BC_ACOK at both pins but they seem gradually go up and surpass 20MOhms.

I'm fairly new to the repairs so I'm not too sure whether this information is adequate.

 

[dukefawks]

At this point it could be any component on the ACOK line that pulls it down. I would go for the ISL6259 first and pray because else it is pretty sure the SMC.

 

[SamMac]

Ordered the ISL chip (should come for Thursday), until then I'll keep at it and update the page once I've got some result.
Thanks for the help so far dukefawks.

 

[smiba]

You might want to order a bunch of them at once since you will probably be replacing this more often on various devices, its one of the must haves

 

[SamMac]

Hey smiba, thanks will do! This is my 4th macbook repair so still getting to grips with it.
I was wondering is there any way i can test that the chip is faulty? maybe by taking it out and checking for specific pins that come out short to ground?

Thank you for your help aswell smiba!

regards.

 

[smiba]

/Technically/ you could solder it onto a circuit board using the same chip just to test it, but why bother? The chip is like $4, its not worth your time, just use a new one!

 

[SamMac]

No Title

What can people make out of this. The boardview I have is for the 2014 model (since the 2015 version isn't easily available).
In comparing the two there is only two resistors below the SMC (however I don't think the third one actually connects to anything so that should be okay). Secondly it seems that the track is somewhat damaged and lastly there is a missing capacitor underneath it.

 

[smiba]

That SMC looks reflowed without having the edge bonding removed...
You can see if the track is damaged by using diode mode. Voltage drop should be 0

Also this area looks really awful

 

[dukefawks]

SMC was reflowed with edge bonding in place, so that probably needs to be pulled and reballed now.
That corroded area in smiba's picture is for Airport stuff so not important right now.

 

[SamMac]

Thank you everyone for your help.
Unfortunately the new chip didn't bring the board to life, doing the exact same thing as before.
Customer decided to go for the more expensive option of going to apple for a replacement macbook.

 

[dukefawks]

There are no "new" chips, you have to take one from an identical donor board.