A broken power supply can cause a number of issues. The most common indicator of power supply failure is to have a machine where the top lights are working but other parts of the machine are not working. Always keep one or two spare. They will fail.

This is how you replace a power supply. You can test it without screwing it in by bypassing the existing one. If it solves the problem then remove and screw in the new one.

Ensure power is unplugged at the wall before doing this.