Power On problem 820-2879

[dukefawks]

3V42 stable? SMC_RESET stable? G2_EN stable?

 

[bighead]

Yes, looks like those are stable even when it's not turning on.

PP3V42_G3H - 3.4V
SMC_RESET_L 3.2V
SMC_PM_G2_EN 3.3V

I also have the 3.3V(P5V3V3_REG_EN) on U7200 all the time.

 

[dukefawks]

How much is PPBUS fluctuating?

 

[dukefawks]

Sense resistors and traces to 6259 all ok?

 

[bighead]

Back to this board. Yes, sense resistors and traces are all ok.

So just to make it clear. PPBUS_G3H goes up to 12.56 it's there for 2 sec and collapse.
I believe the problem is that the PP3V3_S5 rail is all over the place. There is no short on the 3.3V rail.
However if I heat the board just a little bit everything is fine, but when it cools off the problem comes back.

I checked the traces to q7220 all seems ok.

 

[dukefawks]

Replace U7200

 

[bighead]

Didn't solve it. I gave up on this board. Probably a broken trace somewhere.