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820-00165 3V3_S5 a 1V
- Thread starter bjf
- Start date
SMC_PM_G2_EN not being present, if SMC_RESET_L is present, is a sign of
1) A dead SMC.
2) U7501 shorting SMC_PM_G2_EN to ground.
My bet is on the SMC.
On the other hand, SMC_PM_G2_EN missing should NOT result in 1v - or any voltage - on PP3V3_S5. You should have 0v there. So, now I imagine what could be happening is that SMC_PM_G2_EN is present but U7501 is shorted to ground and pulling it down, and is also pulling down PP3V3_S5 along with it. I also find it odd that with a dead SMC you are getting 8.58v on PPBUS_G3H instead of the typical 8.15v I would expect with a dead SMC. But still, partially dead SMC is totally possible.
It's either the SMC or U7501 from the data you've provided.
1) A dead SMC.
2) U7501 shorting SMC_PM_G2_EN to ground.
My bet is on the SMC.
On the other hand, SMC_PM_G2_EN missing should NOT result in 1v - or any voltage - on PP3V3_S5. You should have 0v there. So, now I imagine what could be happening is that SMC_PM_G2_EN is present but U7501 is shorted to ground and pulling it down, and is also pulling down PP3V3_S5 along with it. I also find it odd that with a dead SMC you are getting 8.58v on PPBUS_G3H instead of the typical 8.15v I would expect with a dead SMC. But still, partially dead SMC is totally possible.
It's either the SMC or U7501 from the data you've provided.
bjf
Member
Ok, I replaced U7501 and I have SMC_PM_G2_EN at 3.3V now. Also, the MagSafe light goes green to orange like normal. I lost PPBUS though so I'll have to investigate what changed. I noticed that after I saved the first draft of this post otherwise I would delete it until I check on PPBUS. I'll update this after that.
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bjf
Member
Yes, PPBUS is back to 8.58V. What's odd is that when PPBUS went away, the light switched from green to orange like normal and SMC_PM_G2_EN came up to 3.3V. It looks like the SMC is working fine until U7501 gets power and the rest of the power rails attempt to come up. Or the U7501 circuit is shorting the SMC somehow.
bjf
Member
3V42 is present with U7501 on the board. I think it has to do with PPBUS not being present. When there was no PPBUS present, the light went from green to orange. So PPBUS is triggering something that is causing the light to stay green. And at the same time, SMC_PM_G2_EN is at 0V. And U7501 is not able to function normally.
bjf
Member
I don't actually think U7501 is affecting the light. It appears that when PPBUS comes up, something comes on that affects the light. U7501 is probably completely unrelated, but I measured 1V on PP3V3_S5, so I looked at U7501. But it looks like the real problem is whatever is causing the Magsafe light to stay green. And also whatever is causing SMC_PM_G2_EN to stay at 0V. They may be the same thing. Don't know.