Charger is green, then off, then green, no boot
Hi all.
I’m quite new at trying to troubleshoot logic boards, and have very little knowledge, but I’m trying to learn. So, I received a MBP 13” Early 2011. I don’t even know the conditions of the battery as it’s clearly drained and it won’t charge.
If I disconnect the battery, keep the power button pushed, connect charger, connect battery, release and push again the power button, the machine turns on, the display as well (white screen, no apple no nothing, chimes, fans spinning like crazy and that’s it. Reset SMC, machine dead again. Repeating the procedure and resetting PRAM after the chime also leads nowhere.
I removed the board. Upon connection of a magsafe (Apple original 85W), the light is green for some seconds, then goes off, then returns green and so on looping. Fans: same behaviour. When the green light appears, fans spin. Then they stop spinning (and the green llight goes off) and so on forever.
Following Louis Rossman’s videos and reading a few forums I started taking some measures, and here they are:
F6905 - 16.8V
U6900
- Pin 1 - SMC_BC_ACOK_VCC - reads 3.48
- Pin 4 - SYS_ONEWIRE - reads 2.91
- Pin 5 - ADAPTER_SENSE - reads 2.90
U6901
- Pin 1 - SMC_BC_ACOK - reads 2.36
- Pin 2 - SMC_BC_ACOK - reads 2.36
- Pin 4 - SMC_BC_ACOK_VCC - reads 3.48
- Pin 5 - PP3V42_G3H - reads 3.48
- C6908 - Pin 1 - PP3V42_G3H - reads 3.47
U7000
- Pin 2 - CHGR_DCIN - reads 16.5
- Pin 3 - CHGR_ACIN - reads 3.9
L7030’s reading goes up and down from 12.5 to 3.4, continuously
I then started taking some measures of a bunch of resistors and really got puzzled. I’ll explain why.
R7012 - 0.99 (should be 1)
R7010 - 28,3 (should be 30.1)
R7011 - 9.22 (should be 9.31)
R7013 - missing (should be 1)
R7015 - 100.2 (should be 100)
The issue here is the missing R7013. On the schematic there’s a row of 8 components (caps and res), but on the board… instead of said resistor I find two spots, and no trace of solder. It’s not the only case. R7002 seems to be missing as well, and R5011 too. It actually looks as if they were never there so I’m really puzzled. Here are a pic and a screen of the schematic.
Any help is really appreciated.
I wouldn't focus this deep on diagnostic process!
When you have resistors mounted you can't properly measure them this way! Let's not worry about these R7012, R7010, R7011, R7015.
Missing components is always tricky! R7013 is a no stuff. You can tell by the pads are bare. So that too is a red herring as well for R7002 & R5011. If you saw a pile of solder on the pads or burn marks then it might have been a component that failed or was pulled off, not the case here.
由 Dan 完成的
Thank you Dan. So where do I focus? And the L7030 giving me fluctuating readings instead of a steady 12V, what does that tell me? It seems that green light blinking at the same pace of the spinning/stopping fans and fluctiation of that inductor (I think it's an inductor, right?) are related. By the way, I have the same fluctuation in voltage when I measure F7040 as well
由 Massimo Oriano 完成的
I was still writing my answer so I didn't see your update. Fluctuating values is a good clue! So how does this part of the logic board work? How does a voltage get created in the DC realm? Look over the schematics. Go back to your basic digial electronics.
Review the answer below first!
由 Dan 完成的