TOSHIBA laptop 10 vertical blue lines on black screen no boot DC input jack repair

I have a Toshiba P25-S520 laptop.

Started having a problem with the laptop suddenly shutting off with no warning, as if someone just yanked the plug out.

We tore the whole laptop apart, down to the motherboard. Re-soldered the connections on the existing DC power jack, checked all connections, assembled the laptop, tuned in on, PERFECT!!! Laptop did not shut off like it used to, was on for about 6 HRS that night.

Put the laptop away for the night, after work went to switch it on, hit the power button, initial fans would turn on, then black screen with about 10-11 vertical blue lines on the screen, no lights on the base of the computer indicating wireless, cpu, HD, etc, FROZEN!!!

Took the hard drive out and tried, same problem so not a hard drive issue. Checked screen, not screen cuz brightness can be adjusted.

Wiggled the jack with the power cord, and the front lights (indicating power, battery) would flicker, figured time for a new DC input jack (assuming it was the reason). Ordered, it came in, de-soldered the old one, re-soldered the new one, put back together.

SAME PROBLEM!!!

When u hit the power button, laptop tries to start (initial fans) then blue lines on black screen, and it freezes there. No boot to bios, cannot use F8 to go into safe mode. To shut it off have to hold down power button.

WHAT COULD IT BE???

PLEASE SOMEONE HELP ME OUT I NEED TO GET INTO MY COMPUTER!!!