Diagnosing no power on macbook pro

[Jetlabb]

Hey guys,

I am completley new to this and have been trying to learn, so please don't get mad if this is a dumb question!

I have a Macbook Pro A1278 with the board 820-3115. After going through some of the schematics, and using boardview, I have a few questions. So first off, the Macbook will not turn on. I have a green light on the charger so I know the one-wire circuit is working. I have checked the G3-Hot and it seems to be working. But, when I was moving around the board I noticed that on my boardview it says there are suppose to be 4 of these, and there is only 3, one looks like it may be missing. Not sure if this would cause it or not, but I figured I would ask and find out. The image shows it under the microscope.

On BoardView it says it is T29_TMU_CLK_OUT.

This is that on BoardView, the one towards the bottom with a small green circle is where it is located.



Any help would be appreciated. Not sure where to go from here, or what to test next!

[Keenan_SCR]

Re: Diagnosing no power on macbook pro

Thats R3699, in the schematic listed as "NOSTUFF" which I believe means "Not assembled in factory". (Aka DNF - Do not fit or DNP - Do not populate)

[katfish]

Re: Diagnosing no power on macbook pro

What was the PPBUS_G3H measurement?

[Jetlabb]

Re: Diagnosing no power on macbook pro

What was the PPBUS_G3H measurement?

Hopefully I am doing this right, I am completely new to all of this! So I went through and used BoardView to find everything in the schematics. I did find that U7400 were all 0 except for 25 which was 0.02. Not sure if this is good or bad! So these are the components and the voltages I got.

R6905 - 12.58

D6990 - Pin 1: 12.58, Pin 2: 16.89, Pin 3: 16.61

R6995 - 15.3

C6991 - 3.5

C6990 - 16.7

C6994 - 3.3

L6995 - Pin 1: 3.4, Pin 2: 3.5
u6990 - Pin 1: 0
Pin 2: 3.8
Pin 3: 15.3
Pin 4: 16.8
Pin 5: GROUND
Pin 6: Unknown
Pin 7: 3.5
Pin 8: 3.5
Pin 9: 3.5
Pin 10: 3.5

C6999 - 3.5

F6905 - 17.02

R7020 - 16.4

R7050 - 12.28

F7040 - 12.28

R6905 - 12.28

R6990 - Pin 1: 17.02, Pin 2: 16.89

D6990 - Pin 1: 12.28, Pin 2: 16.89, Pin 3: 16.80

R5400 - 12.28

U5010 - All 3.4 or higher

u7600 Had glue or something covering it, unable to test

R7640 - Unable to get reading. 0.00 on all 4?

U4202 - Had glue or something covering it, unable to test

U7400 - All were 0.00 except for pin 25 which was 0.02

R5410 - 12.28

Then I found where it shows what should always be present for S5. I began testing these and I may have found the problem (not sure). Everything was working fine...

R4262 - 12.28
R4263 - 12.33
Q4262 - Pins 1-2 0.00, Pin 3: 11.94, Pins 4-6 12.28
Q4620 Pins 1-2 0.00, Pin 3 11.93, Pins 4-5 12.28

And then I got here and I think this is my problem...

F4260 0.2 but I get 00.4 when doing reistance
D4260 - 0.01

So not sure if this is my problem or not.

So this is what I did, hopefully it is all right, otherwise please correct me!
Looking at the schematics I found the 3.425V "G3HOT" Supply section and tested all the components shown. At the end of this supply it shows "PP3V42_G3H_REG", so I copied and pasted that into the schematics to find where it was. Which brought me to "J30 Power System Architecture". I tested some of those components and that is where I found the U7400. Am I doing something wrong or right?

Any suggestions so far? And thanks for your guys' help so far, I really appreciate it!

[katfish]

Re: Diagnosing no power on macbook pro

R4262 pin 1 is PPBUS_G3H. There are several points on the board to check different rails. Boardview will simply show you where you can find those points to see if something is present/missing.

There's a few rails that need to be present. PPBUS_G3H is one. It should be 12.6 or 12.8 when smc is on. I forget which. But at 12.3 ... that's an indication smc isn't on.

But why isn't it on is the question. Could be many things, including a bad smc.

Check SMC_RESET_L ON U5010 pin 5 to see if it's stuck in a reset state... should be 3.3-3.4v. Find that using the boardview and it will show you where you can find to check for it.

Check a few other rails to see if they are present. PP3V42_G3H, PP5V_S0, PP3V3_S0, PP3V42_G3H. Post back your measurements. Page 7 of the schem lists all of the different power rails. Right now your concern is mostly S0 rails.... without those, you don't get into S3 or S5 states. PM_SLP_S4_L should also be checked.

[Jetlabb]

Re: Diagnosing no power on macbook pro

@katfish - I will get all of those for you! Sorry I couldn't remember my login information!

Now, just to clarify...

The power states. You said I need to worry about the S0 state. I always thought that it went something like G3HOT, S5, S3, S1, S0. If the computer isn't turning on then you wouldn't have S0, correct? I am new to this and am trying to learn at the same time! Sorry if it is a dumb question.

Also, is there a place on the schematics where it tells you exactly what voltage they are suppose to be? I understand PP3v3 is saying it needs to be 3.3v, but what if it is on a 5v rail and two sides are reading 5v and the other side is like 12 or something. Hopefully that makes sense

[katfish]

Re: Diagnosing no power on macbook pro

Yea, sorry ... was in hurry lol. S5 rails ... gotta have those first, then the others follow going up to S0 (on state).

Some rails are obvious by their name, then some have their voltage listed in the schematic. Others, you need to search through the schematic to figure out where they are created. Other times you need a good board to cross check what something should be.

It's a puzzle of sorts sometimes.

[highpulse]

Re: Diagnosing no power on macbook pro

chek schematic for all S3 voltages , they must all be present or else smc wont start the machine . chek if it does at least charge battery !!! very common on does models having current sense issues on charger circuit.