MacBook Pro 820-2262-A (A1261) intermittent MagSafe light

[mikiotty]

Hi everyone!
This is my first post here, I hope to solve this problem with your help. This is my first experience on this type of repair, so forgive me if I make some stupid mistakes.
I have an A1261 17" MacBook Pro (820-2262-A) which has intermittent green light on MagSafe, and when the light flashed I can hear a click coming from the motherboard. The machine would not power on either via the MagSafe of via a known good, fully charged battery. SMC bypass does nothing.

I checked some voltages and got a regular PP3V42_G3H (3.42 volts), a fluctuating PP18V5_DCIN (between 14 and 16 volts) and no PPBUS_G3H. Time to check for shorts.

I initially found a short to ground on PPBUS_G3H, even at J6990 (discovered at Q5315), and started going backwards.
I checked at U7950 and that was ok, I then checked at U5715 and found that pin 3 and 4 of U5715 were shorted to ground, thus shorting PPBUS_G3H via XW7904.
I traced the short back through R7904 and R7906 and found that pin 21 and 22 (CHGR_CSO_P and CHGR_CSO_N) on U7900 are shorted to ground, thus shorting everything connected to them.
Removing R7904 and R7906 (the two shorted rails are interconnected via C7902) eliminates the short on PPBUS_G3H and on pin 3 and 4 of U5715.
Could U7900 be dead and internally shorted to ground? Should I remove it and check if I get no short (not the easy way) or try injecting voltage in some component? Any known bad component that may cause this?
Thank you!

[KvnTM]

Re: MacBook Pro 820-2262-A (A1261) intermittent MagSafe light

This MacBook is well known for GPU failures.
Avoid all MacBooks before 2012 with dedicated GPUs.

Even if your problem might be something else your GPU is most likely dead anyways.... There isn't much you can do besides changing the GPU to a revised one which isn't worth it since the laptop is really old.

[mikiotty]

Re: MacBook Pro 820-2262-A (A1261) intermittent MagSafe light

This MacBook is well known for GPU failures.
Avoid all MacBooks before 2012 with dedicated GPUs.

Even if your problem might be something else your GPU is most likely dead anyways.... There isn't much you can do besides changing the GPU to a revised one which isn't worth it since the laptop is really old.

Yes I know but I don't care. I don't plan on using it as my main computer whatsoever, and even if it fails I'll replace it myself.

Do you have any suggestion on the component that may have failed?

[KvnTM]

Re: MacBook Pro 820-2262-A (A1261) intermittent MagSafe light

Check all "G3H" Power rails. These have to be always present.