820-00923 not turning on

Hello, I have an 820-00923 that came in dead, looks clean no liquid damage. It had a short on PPBUS. after injecting power (removed all FDMF chips) I found a short on U8000, replaced it and now I have 13.07 on both sides of F7000. On L7030 I get fluctuation from 8.4-8.6v but there is no short. On charger I get 20V, 0.04A. Not sure what to check next. Could it be CPU already died from short before?
 
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2informaticos

Administrator
Staff member
First of all, welcome to the forum!

Very likely dead CPU.
Injected voltage goes directly into CPU, through 1V0_SUS.
Do NOT do this ever again!!!
So many times explained WHY NOT in the forum, and people still doing this :(.

CPU could be already fried because of shorted U8000 (on high-side part).
But you've eliminated the lowest chance of being still good...
 
Hello, I have been in the forum before but lost my login details.

From what I understood is that if I remove all high-side mosfets I could inject voltage? How would you suggest to find a short on PPBUS otherwise if board is completely clean? Is there anyway we can measure resistance to see if the CPU is dead?
 

2informaticos

Administrator
Staff member
If you get the same ohm value (to ground) on PPBUS_G3H and one big coil (not only from CPU), guess what that means???
 
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