820-3476 randomly not getting P3V3S0_EN

[bjf]

This board is switching between 3.3V and 0V on P3V3S0_EN (from PM_SLP_S3_L). It will work fine and the screen will come on and then next time I turn it on it will have no P3V3S0_EN (no PM_SLP_S3_L) and 3V3_S0 gets stuck at 1.9V. The only damage I can find was on the via leading to R8319. I fixed that. I replaced U8030 just to rule that out. There are no shorts that I can find. Everything is measuring fine. Is this familiar at all? I'm not sure what's happening with this.

 

[2informaticos]

Are you using original Magsafe 2 charger?
Don't use 1-->2 adapter.
Same thing on battery only?

 

[bjf]

Yes, the same original 85W MagSafe 2 power adapter I always use.

I noticed that PM_SLP_S3_L does come up once every time I plug it in and drops down immediately.

I tried it with battery-only a number of times and it was turning on normally. But after going back to trying it on adapter-only, it's also working consistently now so I'm not sure it's telling me anything.

 

[2informaticos]

If PM_SLP_S3_l pulse only once, could be SMC sensor issue.
If starts to fail again, check if always starts in SMC bypass mode.

 

[bjf]

Any idea which sensor it might be? Or is it just possibly one of many? The only corrosion or damage was a little bit on the battery connector and near the keyboard backlight connector.

 

[2informaticos]

If you get pulse on all coils, then can be any Isense, or Vsense sensor.
Less probable to be temp sensor...