Acer Aspire 5551 - AL-5911P motherboard - won't turn on

[capow]

Hi to all!
This is my first thread on this forum and I am a newbie in the chip component level repair.
I think the users skill in repairing will help me to solve my problem.
I'm trying to troubleshoot a AL-5911P motherboard that won't turn on. (I have uploaded the schematic)
The fan starts to spin and 2 seconds later stops.
I have already found the PQ30 mosfet shorted (AO4456), on the circuit of the buck converter PU8 (RT8209) that feeds the +NB_COREP power rail.
Without the PQ30 mosfet on board, the +NB_COREP power rail shows dead short yet, over the PJ8 jumper. I had opened this jumper to separate the buck converter from the rest of the power rail.The short is on the side to North Bridge chipset (AMD RM880).
I tried the smoothing cap C189 (330uF) and it is good, no short, good ESR.
My questions are: is it possible that, if the power rail to the NB is 10A, the chip shows a short on this rail?
Or...Is the North Bridge shorted?

Thanks

[highpulse]

Re: Acer Aspire 5551 - AL-5911P motherboard - won't turn on

ehhe its not short , but NB and cpu will be in low ohm state , inducting people thinking its in short . , well it could be .. since this IGP suck big time .. but there are other test you can doo , tell you resistance to GND on all big coils . and try to see voltage you got on each coil , in the moment you try to turn it on
let us know voltages and impedances

[capow]

Re: Acer Aspire 5551 - AL-5911P motherboard - won't turn on

Thanks Highpulse,
I will test every voltage on the power rails and I'll post their value as soon as possible.
To to these tests I will disconnect the jumpers on the power rails, to separate each converter from the rest of it's power rail, as I did whith the +NB_COREP. I mean, first thing first, to check if there are other components shorted on the converter side.

[dellxps15]

Re: Acer Aspire 5551 - AL-5911P motherboard - won't turn on

i have a 5551 and nb fail very much. reball it.