Question Upgraded to 6700k

Mar 9, 2019
Hello toms hardware forum. I have a problem with bought 6700k. I bought an nzxt h500 case so i decided to buy aswell a new cpu. Bought it second hand from a lad that tested it 3 days before he handed over to me (well atleast he said that), he was selling his pc part components and I can see from other people responces that the parts are working. I moved all my parts from my old case to new case and put in i7 6700k to motherboard, i had to clean cpu a little bit with isopropyl alcohol as there was some marks of old thermal paste. After i switched on pc it started to countinously switch on and off after couple seconds, i tried to reseat all the components and cables again , aswell i cleared cmos, changed ram slots, left everything unplug except ram motherboard with cpu and graphics card. After fighting with it for couple hours I gave up and put back in my old i5 6600 and everything went back to normal. Is the cpu gone? Or is there anything that im missing ?

Parts im using:

gigabyte z170x gaming 7
corsair vengance 3000mhz ram (tested aswell with my old 2400 gskill ripjaws v)
seasonic focus gold 650w
gtx 1070.