820-2523 "temporary" short on 5V_S3 and 3v3_S5

[Fizzl92]

This 820-2523 sometimes turns on but mostly it is dead. Sometimes it turns on but has a black screen. Except for a lot of smokey black dust the board looks fine. I checked power rails and PP5_S3 is missing. After i disconnected the charger it is shortet (0.02V in diode mode) but it is slowly recovering as long as the board is off. It comes back to 0.4V. If i plug the charger back in and disconnect it again it is shorted again. I injected voltage and U7201 was getting hot. I replaced it twice but still the same. Also the same happens to PP3V3_S5. Now i am stuck here...

 

[dukefawks]

That is normal and is just residual charge on the gates of the FETs. I honestly have no idea what this could be as it could be anything. Seeing it is intermittent it could very well be corrosion under something. But is could be anything really, not looking good for this antique.

 

[Fizzl92]

ok, thanks. So as the "temporary short" is ok and not the problem here i kept searching and - what else could it be - the 5V_S3 enable and PM_SLP_S4_L are missing... Are there areas on this board (like U1900 on the 820-3437) that i could check?

 

[dukefawks]

No real known issues with this board. If this does intermittent crap like this I doubt it will be worth your time. Probably will end up a no fix and a lot of wasted time.

 

[Fizzl92]

Ok... Thank you for the help