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820-00165 3V3_S5 a 1V

bjf

bjf

Member
Liquid-damage. PPBUS 8.58V. Has MagSafe light. 3V42 is good. U7501 enables are at 0V. SMC_RESET_L is at 3.38V. Not sure where to go next with this.
 
bjf

bjf

Member
No shorts anywhere. SMC_PM_G2_EN is not present. It's at 0V. I also just noticed that the MagSafe light is not turning orange. It's staying green.
 
bjf

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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dukefawks

Administrator
PPBUS voltage still at 8.6V now? I suspect bad soldering or another bad U7501. Also inspect traces especially to the VIN pin. Resistance to GND on 3v3_s5?
 
bjf

bjf

Member
Yeah, I save that post and then realized PPBUS was gone. I'll figure it out and update this.
 
bjf

bjf

Member
Ok, so I switched out a third U7501 and it's back to 1V on 3V3_S5, 0V on SMC_PM_G2_EN and Magsafe stuck on green. So apparently, something in the U7501 circuit is killing SMC_PM_G2_EN. I've checked for shorts and failed components and can't find anything.
 
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dukefawks

Administrator
PPBUS checked? Green light on charger would suggest SMC is not running or 3V42 is not present. Crap under SMC possible too.
 
bjf

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

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.
 
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dukefawks

Administrator
Even if you short out PPBUS the green/orange light should still work. Again I see no way for U7501 to affect the light.
 
bjf

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.
 
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