So, if Neo Geo forum posts are to be believed, you can't really trust the sticker on the bottom of the console to indicate what power supply you really need. And if you stick a 9V power supply into a 5V system, you run a very real risk of smoking the motherboard. Meaning your only option is to physically inspect the board inside.
An old credit card made short work of the rubber feet and here's what was inside:
Thankfully the board is very clean and has had no previous work. I took one look at the BIOS chip, and yeah I'll be desoldering and lifting pin 2 and soldering the Unibios chip on top of the old one. It is surrounded by tiny, delicate traces and this isn't a $1 Genesis football game.
Here's the power switch area -
Now what's kind of interesting here is that the system is labeled to "USE PRO-POW AC ADAPTOR ONLY" which implies a 5V supply. But there's a 5V voltage regulator.
Anyway, that means I can just toss a readily available Genesis 1 9V power supply at it and we're done here. This was sold as, "Occasionally, power switch contact is bad. Occasionally, the power switch turns on and off repeatedly." Maybe the seller had it hooked to a 5V supply? Maybe I won't lose ---my bottom--- on this?
Phones can do anything except hold me at night and take photos of things up close, but you get the general feeling here that we're not dealing with cracked solder on the power jack:
This, however, is giving me some hope. I have had issues with old consoles turning off and on randomly, and it's been corrosion on the power jack.
Anyway, a little scrape scrape with a needle and we've got shiny metal again.
The power supply... av cable... joystick... and actual game are all in the mail.... so no testing this thing for awhile....