More information about the power and connectivity was requested, so here it is!
First, I am operating my power supply from a VARIAC on a ground isolated transformer. Occasionally this includes a dim bulb tester to spare untested machines from burning themselves out on first boot.
After this rudimentary protection circuitry I have a regular old budget ATX power supply:
This requires a modification to the sensing line, which I hard-wired to ground so that the power switch on the back of the ATX power supply turns it entirely on and off. This is a convenient reference to get started with a custom switch.
After that I have a custom power monitor connected to a remote relay. The remote relay turns the entire protection circuit on and is located next to the monitor as the mint-green circular button on the lower left:
The outlet connects to a power bar and is basically the "output" plugs for this whole setup. The on/off switch will turn the monitor and supply voltage.
Finally, coming from the ATX adapter I described in my previous post, I have these three additional cables which I connect the RGBtoHDMI to:
These are the connections from the logic board to the RGBtoHDMI:
Red "V-Sync" from Logicboard to RGBtoHDMI Vertical Sync
Green "H-Sync" from logicboard to RGBtoHDMI Horizontal Sync
Gray "Video" from logicboard to "Green 2" on the RGBtoHDMI but you can use any color channel if you configure your RGBtoHDMI accordingly.
This is the RGBtoHDMI profile I created for compact macs. This will work on the following machines: