If it's very picky abvout what PSU it will post with, it's also possible that the VRMs are going/gone on the motherboard which causes it to fail on a power supply who's 5V or 12V lines aren't within a certain range. It doesn't even have to be the middle of ATX spec, it could be on the high or low end but still within spec.
Does the ebay PSU power a different PC without any problems? If so then you're probably looking at something other than the PSU as the culprit.
__________________ ASUS ROG Strix Z370-G Gaming (WiFi AC) / i7 8700K / 2X 8G XPG Spectrix D40 (3000) / XFX XTR 750 / ASUS Strix GTX 1070ti AZZA Titan 240 / Custom WC / Intel 730 Series 480GB SSD / Intel 760p 512GB NVMe / Seagate Barracuda 1TB / ASUS SWIFT PG279Q Asrock AM1H-ITX / AM1 Athlon 5350 / 1X4G Gskill PC3-14900 / Intel 6235 Wi-Fi / 90W Targus Power Brick / Uncased 256GB Sandisk Z400S SSD / Mini-Box M350 / 24" Westinghouse L2410NM |