A few months ago, I built a pc which worked perfectly fine. Suddenly one day i tried to turn it on and it wouldn’t post. I noticed a red cpu light and a yellow dram light was on. I tried resetting cmos, checked all the cables were in properly etc. I didn’t know the issue so i took it to a repair shop who said it was most likely motherboard or cou failure. I have just bought a replacement mobo and cpu of the same models and fit them both in but it didn’t fix anything. Please can someone help me?