XBox 360 S does not (start/complete) boot sequence.

Got the console from someone who claimed the unit would work and then freeze up after a few minutes.

He needed the original power supply for his replacement console, so I bought one to use for myself. One plug tested at 5V. The other tested at 12V. I don't remember measuring current. The console AC adapter was plugged into a surge protector sharing a TV, an HDTV antenna receiver, and a laptop AC adapter.

I used an HDMI cable which was working on an original XBox 360 console and then an OEM component cable.

I can open and close the disc tray with an audible beep.

Hitting the power button gets me a green light and I'm forgetting whether there was a beep.

Using an original XBox 360 wireless controller, when I pressed the XBox Guide button to power it up, all four quadrants on that button started blinking. I replicated the same results using an original XBox 360 wired controller over several USB ports, but not all of them.

I believe the fan was spinning in all instances.

The TV still has yet to receive a signal (whether on HDMI or component).

I also noticed ... an X-clamp! ... in the teardown guide. After fixing several original XBox 360 consoles, I really want to get rid of the 360S' X-clamp and replace it (and perhaps the thermal grease).

What else should I try and examine in order to repair this console?

Thanks for reading!