Getting power to my new Defender { UPDATE }

[BathtubAmbassador]

(ignore this, read update) New guy here, been watching John's channel for a little while, but I never owned a stand-up until I made a for a Defender. It's a small project machine, but here's the - I know it has a bad 4116 RAM IC b/c the previous owner said so. He got the info via the start-up diagnostic. However, the power cable is cut at the end. (which I knew about when I got it.) I was wondering how he got the power to the machine to check the RAM, and that's when I noticed a small wall power outlet inside the machine near the PSU. I can't find any documentation for what the heck that is. My question is, what is that power connector, and can I use it to power the machine? I can post a picture if required.

UPDATE: I got power to the machine! more details forthcoming

[BathtubAmbassador]

LINK TO IMAGE

I got power to the machine, but I'm stuck here. Sound is working, I can activate the sound test with a pushbutton. It freezes at this screen on bootup. Sometimes all 4 LEDs are lit and stay lit, other times the first 2 LEDs on the ROM board are lit. Any ideas how to proceed? (sorry if this is a double post or something)