A couple of months ago, my cousin gave me his old xbox 360 with the red ring of death. So I opened the case and made a few minor adjustments, nothing major and put it back together (but it didn’t have a fan assembly but I know that’s not the problem). So I hooked it up to the power block and hit the power button and the green light will just flash (once) on the Xbox, and the light on the power supply turns red. This happens every time I power it up. I know that the power supply is fine because I use it for my other xbox. If anyone has any ideas of what may be causing this and how to fix it please help!
PS, I know neither cooling nor having no input in the fan assembly power input is the problem