Notebook Acer Aspire 5551. No initialization and weird behavior.

Purchasing:

Notebook purchased for cheap from OLX with folowing description:

Used by childrens over 6 years, now it has a problem with power button, somtimes it won`t turn on and can shutdown without any reason. Also there is broken body at the hinge.

The seller says that a service guy even did not take it to repair, because there might be a problem with some bridge and rapairing can be irrational...

Diagnostics:

First boot runs without any symptoms just fine.

There was installed 5 antiviruses, several anti spy programms lot of cleaning/speedboosting apps and other crap. The windows was full of lags.

I have installed fresh windows and made some tests. Everything works normaly.

The next day notebook wont start, just blowing fan and flashing power LEDs.

I have been adviced to heat up the north/south bridge. No effect.

When I resolder the EEPROM, the system starts and begins works normaly.

The next day new symtoms appears. The notebook wont go initialization again, but sometimes it runs and works normaly until reboot.

So I decide to flash a new BIOS and the problem is gone, everything works.

New problem appears in few hours. The immage begins to blinking just like a north bridge was damaged. Weird thing was that a LEDs was blinking just like an image. In 30 seconds of artifatcs the image is gone to black screed also with LEDs was barely visible flashing. Also weird was that an image normaly works on external screen, and the system works normaly in this condition.

After some diagnostics on motherboard i have found burned SOIC8 MOSFET that generates +3VALWP. Replacing it dont give any effect. +3VALWP was pressent, but the +3VALW has a veird behaviour.

On powering on, the +3VALW rises to 3.3V and slowly drops voltage to 0 in 5-20 minutes. When voltage drops to 2.3V, the flashing problem begins.

On the schematics, +3VALWP and +3VALW is connected by solder jumper. Resoldering it dont give any effect.

Problem was solved by bypassing theoretical loose in the motherboard layers with a wire, which I connent the +3VALWP output to a biggest trace on +3VALW line.

Now the laptop works perfectly with several days runing NFS Underground.

Later I have replaced thermal paste, fix some body elements and strongly glued screen hinge.

Resume:

Flashing new BIOS

Replacing +3VALWP power MOSFET

Bypassing lose contact on +3VALW line

Changing thermal paste

Body repairing

Replacing RAM to 2*2 Gb (+200 UAH)

Installing fresh OS