I actually found a power brick that's got this plug but it's 24v, so I think I'll just clip the end off.
I have a connector box Va (five a) and it's labelled for 7-12V DC. Below is a picture of it's current state:
(uploading now)
edit: here you go:
Left (pin connected to the trace) is power. Right (pin that doesn't appear to go anywhere; it is connected to the ground plane at three points) is ground. There is about 13V coming out of there since the wall wart is so lightly loaded (rated for 1A, actually delivering ~0.15A), and all the power chips aren't even hot so I call it good for now.
Here's another picture where you can see the polarity label on the cable:
https://farm6.staticflickr.com/5599/15529261151_b36aaa08bf_o.jpg (make sure you click. I think this picture is a little nicer)
On the PCB, 1 is GND. 2 & 3 are power. The shell connector (shield) is not electrically connected to anything.
Since pins 2 and 3 are connected on the PCB you can think of it this way:
small pin is power, large pin furthest from it is GND.
The solder looks ugly because it's a mix of the lead free stuff they used and the lead solder I used. I was too lazy to properly remove all the solder and it works so I don't mind. I will eventually remove this and switch to a proper plug so I can close the box all the way.
What did you use to determine the pin-out of the connector?
Just my mad skills at engineering. I just looked at the PCB. Power is fused & GND connects to the GND plane. Simple as that.
I have a connector Box IV. On the bottom of my box it lists "9VDC 1,35A max". I tried following the pinout below(with 9vdc instead of 25) but I don't get any signs of life.
Show Image
I believe this is consistant with my picture above. Not sure why it didn't work for you.
I see a light pipe near the connector does it light up when you power the box? Assuming it lights, does it need to be connected to a keyboard to light up?
On mine it lights up green even if nothing else is plugged in.