I removed my AMD CPU cooler to replace the thermal paste, and afterward the computer stopped displaying anything. The monitor gets no signal, and the mouse and keyboard do not light up, although the PC can still charge a phone through USB. I've reseated the RAM and graphics card, checked that the CPU and socket pins appear intact, and removed the CMOS battery for a few minutes before reinstalling it. I haven't yet left the system powered off for several hours or taken it to a technician. What should I check next?
3 Answers
If you only removed the cooler and didn’t disconnect the main power cables, excessive cooler pressure or an imperfect CPU contact is still possible. Remove the cooler and CPU, check the socket again, clean and reapply the paste if necessary, then reinstall the cooler with light, even pressure. If you’re uncomfortable checking the power connectors or socket yourself, having a technician inspect it is a sensible next step.
Start with the basics: test with only one RAM stick installed in the slot recommended by the motherboard’s layout, then try the other stick if needed. Reseat the 24-pin motherboard cable, the CPU power cable, the graphics card, and its power cable. Also check that the power supply switch and front-panel power connections are correct. Since the cooler was just removed, loosen each cooler screw slightly and tighten them gradually in alternating turns—too much or uneven pressure can sometimes prevent POST.
The system is second-hand and didn’t come with a motherboard manual, so I may need to identify the correct RAM slot by trial and error. I’m not very confident working with the power cables, though the CPU and socket pins look intact.
Inspect the CPU socket very carefully under a bright light. Even one slightly bent pin can cause a complete failure to POST with no keyboard or mouse power. If the pins look normal, reseat both ends of the 24-pin and CPU power connections, confirm the CPU fan is connected, and check that the cooler is mounted evenly rather than overtightened.
I didn’t unplug the cooler because its cable was long enough to leave connected while I applied the paste. I’ll probably have a professional inspect it in person rather than risk damaging anything.