PC won't power on. At first, the green light stayed lit on the back of the power supply, but now it only flashes (no beeping) for a second or two before going dark. Signs lead to a bad power supply, from what I can tell. Are there any troubleshooting tests I can do to diagnose it further? I tried searching for a power unit by using the PC model name and also by using the part number on the power unit: DPS-460DB-3 A, but the parts brought up on eBay, Amazon, and Rakuten are a little vague about whether it is the correct replacement unit. I know I need to make sure it is 460 watts or more, but I don't know whether there is a specific power supply unit I must purchase or if any will work as long as it has the right amount of watts.