MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

[mon2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

Measure the resistance from the arrow heads 1-1.

Then 2-2.

What are the resistance readings for each ?

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

Sadly I lost first resistor so I will need to replace - it blew away

For second on the right: 00.5

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

For first on left: 00.5 [resistor missing]

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

Whilst looking around board, I did find broken trace but elsewhere.









Could this be causing any issue?

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

^ Around U9950 - I am not sure what this does.

It looks like trace broken between highlighted red points, there is point there looks like it goes to other side of board? I could not scrape anything away and could not find any continuity from it to either points. I tried to scrape off some trace on right and also no continuity to there.

[mon2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

See attached.

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

see attached.

u9950

[mon2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

See attached.

I believe this is the trace flow - from pin # 7 of U9950.

Respectively, it does not matter how the traces flow on the PCB itself as long as you can rebuild the same connection.

You have enough meat from Pin # 7 trace that is broken to solder a thin wire and connect it directly to the target point = pin # 5.

Update - you have meat (actual test pad you can solder to) on pin # 5 trace.

You have meat on pin # 7 trace.

Just solder a small wire onto the pad on pin # 5 trace and mate it to pin # 7 - done.

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

Hi mon2,

Yes I will fix this, is this likely to be causing the problem?

Can we do more testing in the meantime whilst waiting for the resistor replacement for the other component?

[mon2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

This could have been THE show stopper. Of course you still need to replace and stuff the 10 ohm resistors - suggest 1% tolerance if available. The engineers expect this resistor value to be present in series to the current sense resistor. Based on this value, they have knowledge of how much current draw is too much to shut down the unit.

You are facing a shut down event so it is quite possible that U7000 is shutting off PPBUS_G3H (a critical rail) due to the missing current sense loop.

At this time, can only wait for the parts to replace and see. The area you shared appears to be toasted - any other damaged traces ? If not obvious, just wait for the replacements to move forward.

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

Hard to say as do not have any other unit to compare to.

R2113 is missing.

R1848 is missing.

R2913 is missing.

R1922 looks a bit dodgy?

R2067 is missing.

R1843 is missing.

R2155 is missing and one of the pads looks gone?

Are any of these vital?



Rest of board looks clear, please let me know if you can see any other issues here.

[mon2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

R2113 is missing - for JTAG TCK parking of the line when not in use.
Ok to skip it.

R1848 is missing - not sure but is GPU related.

R2913 is missing - unable to locate this one in the schematic.

R2067 - is a pull-up; if this signal is open-drain then it is required but skip for now.

rest - for now - just try to run with the above repairs. Keep the thread posted with your updates.

Need to run and find a dress shirt for my son's bday party...he wants to dress up for some viral video thingy.