Someone please help PS4 3sec BLOD

A friend asked me to fix his PS4 a few weeks ago and to begin with when you power it on blue light would pulse for 8sec a beep 3 time and cut off iv tried literally everything bought a new motherboard thinking it was a solder connection problem on the gpu now it will come on for 2sec and power off as of now iv bought and replaced power supply , motherboard and paired optical disk drive, cooling fan, and the hard drive lol everything except WiFi antenna and still no luck if anyone has ANY suggestions it would be GREATLY appreciated. Ps this is the first device iv ever wanted to just throw into the ocean an forget about