I removed and cleaned both the CPU and the socket with Isopropyl alcohol and now it works just fine. I installed ChromeOS Flex on it and its also much faster than with Windows.
The PC does not Post and has error code 1,4 and amber light and pressing the power button shows code 3. It is a Core 4 with 4 GB RAM.
Dell Optiplex 780 SFF error code 1,4 and code 3