Google for. "jamma pinout". One lead on one of the 5v pins and the other on one of the ground pins.
I left pick'n mix running for a few hours on my 4-slot during a party. No one played the machine, but it never crashed. The 161-in-1 came with the cab, and attract mode is the only thing I keep it around for. That feature of the Unibios is just that cool!
Yup, PICKnMIX is an awesome feature. I like to leave it running in the background when I'm doing stuff around the house. It attracts me, lol. I usually end up playing something. It's also fun to try to place which game you're hearing at a given time. I'm surprised by how many I know, just by sound.
As for the jamma pinout, yup, I found it. Didn't find a YouTube video specifically about testing at the edge connector though, so I went ahead and made one for the next guy:
It turns out that the big power supply in the back runs my board (I think maybe the one up top runs the monitor, or just the marquee light?) and the voltage read at 4.3. Unfortunately, 4.7v was as high as it would go, so I still don't know if a full 5.0v would be the fix to my problem. Oddly KOF '99 didn't freeze during the attract mode, but Samurai Shodown 1 still locks up, no matter what. It also errored out on Spinmasters while I was making that video (not shown), and that was recorded after I maxed out the juice.
I was afraid I was killing it while I was turning up the power. Speakers kept sputtering and the screen went black, but I was already doing it so I kept going (as far as it would let me). Obviously everything is fine, but it was harrowing. LOL
I also noticed the screen image contracting more on all white screens, but maybe it always did that and I'm just hypersensitive, looking for problems I might have caused