Xbox one S Powers off after 10-12 seconds

I have an Xbox one S console which I have had for at least 6 months now, I bought it on eBay and figured it would have been an easy fix. I did read the description to see what was wrong with it, they had said it would turn off after a few seconds, which I thought was around 5 seconds or so, but apparently is 10 seconds. I had bought an Xbox one S before which was a very good deal that I couldn’t pass up. Which was one with a bad HDD. I was hoping to find another one which was a bit cheaper but was in very good condition. I did however find the problem that was wrong with it, a bad power mosfet. I had bought a heat gun tool, some flux and a new mosfet. When I did get the old one off I was thinking ‘okay just need to put the new one on’. I have watched a lot of YT tutorials on how to replace the chip. I was going to take it to a shop but had a already bought the new chip and didn’t think they’d let me bring it in since I had taken it apart. I am not really worried about this Xbox, but my brother would like to have one and play online with me.