[Paul R.]

Cables and connections are all checked in triplicate, but, I can also check power supply voltages. (Fluke 8060A meter)

Thing is, most everything that should get warm does get warm, about as expected. But an individual rail somewhere could be down...

[Gideon7]

Does the Num Lock key LED turn off and on when you press it? That would mean that most of POST had completed and the CPU is working.

[Zhang Fei]

[Cables and connections are all checked in triplicate, but, I can also check power supply voltages. (Fluke 8060A meter)

Thing is, most everything that should get warm does get warm, about as expected. But an individual rail somewhere could be down...]

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The Achilles heel of gaming rigs is power. The display card vacuums up huge amounts of power. My personal experience with computer gremlins has been that power supplies are always a good place to start. Gaming rigs are bleeding edge, generate huge amounts of heat. That causes premature component failures. If there are dust bunnies inside the power supply, consider clearing them out with a can of compressed air.