Computer shut down and wouldn't start so I opened it and cleaned some dust. It started but screen was blank, so I checked if all cables were connected and saw one loose pci cable which I thought was another for the GPU, but with it plugged in it won't start at all. It's a self made rig I bought used from a friend and has some extra fans. It also smelled a bit burnt before shutting down. Can anyone diagnose what is broken and if it can be fixed? Thanks for all help and feel free to ask more questions.