Can a PSU wipe out the graphics card, mobo or the CPU or all?
Yes, it's all powered from the PSU, so it can damage anything.
Standard diagnostic sequence is to remove everything but the CPU from the mainboard, and have either the onboard beeper provided or a small system speaker connected to the SPKR terminals, so you can hear POST beep codes, then follow a process of elimination with a complete power down between each stage of trying adding one component.
So in other words, remove/disconnect all peripheral cards, RAM, drives, and start up the system. If the Mainboard/CPU combination is operating, the BIOS should issue an insistent beep code complaining about the missing RAM. If this doesn't happen, suspect damaged mainboard, CPU or both (CPUs seldom fail). If the board beeps angrily something is working, you can check the manual to see if the code is for RAM not found. Then power down and one at a time add RAM, in which case the beepcode should change to indicate missing video card, if so add video card, see if POST shows... If yes, connect drives one at a time, see if one stops it from booting...etc
Edited by Platypus, 26 May 2016 - 10:50 PM.