On eBay I sold a fellow a 1080TI that I got refurbished direct from Zotac. I didn't use the card first other than to do a 3DMark 20 minute stress test in my gaming machine to make sure it worked before I sent it out. It passed just fine as expected. I boxed it back up and sent it to the guy. He reached out to me and told me there was a problem that anytime he tried to launch a game his PC locks up, or goes to a black screen and has to be restarted. He opened up a return eBay claim, and I reached out to him and asked if we could talk first to troubleshoot the problem. In the meantime he closed the return claim stating he took the PC to his local computer store and they said it wasn't the video card and they got it working. I reached back out to him and asked if it was his powersupply out of curiosity. He said the problem was still there, and the computer store didn't actually fix it, they just thought they did - but since he got the machine back it hasn't worked. We facetimed and he showed me the issue on Epic Fortnight. He said he originally had a 500 watt psu with a 2060, but that wouldn’t handle the 1080Ti card, so he bought a brand new 750 watt EVGA power supply (he bought on amazon) powering an AMD Ryzen 2600 watt system. I had him download CPU-ID powerMAX stress test and his CPU doesn't lock up when it is tested on 1 minute AVX test -- but the powerMAX GPU stress test locks up his PC in less than 1 minute. Either the video card went bad, or the Power Supply can't handle the extra power draw of the 1080TI at load is my guess? At idle the PC works just fine for everything. When you launch a game within 30 seconds it'll lock up. I've never heard of a video card that works fine, boots fine, works fine for desktop use, but locks up when you go to a game --- unless it isn't getting sufficient power - so that would indicate Power Supply to me - especially since I tested it successfully before I sent it. However, I'm not trying to leave a guy hanging, and if it's the video card that is bad I'll take it back. EVGA is a good brand PSU, and 750 watts should be more than enough for that system - so it would have to be a faulty PSU or that should have been sufficient. He doesn't have extra parts to test with, and no local friend to swap hardware with(and he already sold off his 2060). He's going to try to take it back to that computer store and see what they say. Otherwise I told him he could just return the video card to me for a full refund, though he may have the same problem with another card if it is the power supply. FWIW - temps seem fine for both CPU and Video Card before the lock up occurs -- we were monitoring them with powerMAX and CPUID's hardware monitoring software. Your thoughts?