ASUS N55SL - Quanta NJ5 DA0NJ5MB8C0 - ASUS N55SF - GT555M CUTS OFF RANDOMLY

Hi everyone...

I've bought a ASUS N55SL-s2019v which was turning on with blank screen...
Re-programmed & changed SPI & it finally posted,installed windows,drivers & let the battery charge...When the battery was fully charged I've heard some kind of popping sound,however checked the board under microscope & there was nothing blown...The battery is not charging since then (windows says 0% & charging) but charging LED lights red...Battery gives me 0V on terminal, so I think it's dead...When it's powered without the battery & CPU / GPU has some usage it toggles between "BATTERY/AC MODE" over & over sometimes...It came with 65W 3.42A charger, which is not from that laptop(think it requires 90W 4.75A), so thought that was the case & connected to my bench PSU, but still the same...Also replaced MB39A132, but didn't help...

BUT the main problem is when stress testing the GPU ( GT555M MXM Card ) it cuts off power immediately & then turn on back again (however it's OK when the GPU is underclocked)...The temps are no more than 60°C so it looks like some rail is unstable...ALSO PLS NOTE THAT I'VE USED BIOS DUMP WITH 207 REVISION WHICH LOOKS LIKE IT'S ONLY FOR SF SERIES & LATEST REVISION FOR SL I'VE FOUND IS 204...Can't find any schematics or boardview anywhere...Could You point me what should I check???

A little update...

The coil resistance on BAT rail was a little bit higher than it should be, so de-soldered & found that the copper wire inside was cracked...It's been replaced, however problem with BATTERY/AC mode still not solved (at least I know what made the popping sound )...Could anyone help me, at least where can I get schematics???

OK...The "BATTERY/AC MODE" toggle is fixed now...But still need to fix that unstable rail...Looks like it doesn't have enough power, cause when I set 20V on my bench PSU & underclock GPU it seems to be working OK...It draws something above 4.5A when stress testing...