820-02098 5v no liquid

[Patricia]

Hi to you all

I got a 820-02098 board with no liquid and in really nice condition (not even dust) that just died during a Word document according to the client.
I get 5v and 0.000A on the charger...
I have no knowledge about this board (all new to me) but this is what I have so far
PPDCIN 5.195 v diode mode-0.557
PPBUS_AON -0.322. diode mode- 0.035 , resistance to ground 34ohm
PP3V8_AON 0v. diode mode-0.153
PP1V8_AON 0v. diode mode -0.443
PP5V_S2_MAIN 0v diode mode -0.395

No big coils have the same resistance to ground as PPBUS_AON , mostly around 300 ohm....
Any help is highly appreciated

 

[2informaticos]

0.035 is very low for PPBUS_AON.
Remove F5200/1 and see where the value remains.

 

[Patricia]

On the system side (pin 2) it remains the same 0.035
on the pin 1 its now 0.545

 

[2informaticos]

I suppose you also get correct C5250 voltage then.

So your problem remains on the PPVUS_AON side.
May have a shorted MOSFET, or power IC connected there.
If you can discard any issue with a secondary power supply, then is safe to use voltage injection method.

 

[Patricia]

Thanks 2informaticos

yes on C5250 I have now 12.29v

Ok I will inject , any advice how high I should go Tried 1v but nothing got hot ....

 

[2informaticos]

With 34 ohm resistance, 1V doesn't help at all.
The problem may appear if you escape some short on high-side of a secondary power supply.
Injecting higher voltage may cause letal damage then.
If your checkings are correct, increase the voltage slowly and use an IR camera.
Even 12V may not generate sufficient heat to find it with the fingers.

 

[Patricia]

Well it seems I located the problem , UG400 (cd3217) is the only thing getting hot ,
went over the board several times and according to my Qianli thermal cam only one corner
of the UG400 reacts to injection , I injected up to 2v.
Thanks again 2informaticos