Anyways, I wanted to use the built in power supply for my project and not provide an external one. Turns out, it's similar to ATX power supplies where it won't turn on unless you do a little dance. For an ATX power supply, there is a well documented PWR_ON pin to tap to ground. And voila, power. For this power supply, no documentation I could find.
So with a little bit of poking and testing, I found out it's super easy. I checked the pins on the router board itself and noticed that the +5v and GND had continuity. So I pulled out a high wattage resistor (to hopefully not blow something up if I was wrong) and connected them. Ta-da. That's how you turn on a Cisco AA20270 Power Supply. Now I have 12v and 5v supplies to use.
So... it's pretty obvious with this power supply to tell when it isn't "on". It has an audible clicking at about 3.5Hz and you don't get a constant power. Th clicking is essentially the power supply checking if it can enable fullpower or not.
Simply tap that GRD to a +5v pin, and you're good though. Here's the clicking sound and showing you get constant voltage once you connect +5v to GND.
EDIT: I think It just needs some sort of current going rather than just connecting wires. The connecting wires actually carry a current through them so you can't just do a basic connection like with an ATX power supply. Use a high watt resistor or an actual load.
