SNES grounding issues, driving me nuts

[realyst]

I've been working on making a portable SNES mini. But have run into an issue.

I had burnt the internal fuse when I tried powering the unit with a 9V battery pack, and have bridged it(so you know what that thing in the pic is. Issue is, even though the SNES mini works fine when powered via the usual 10V SNES power adapter, if I try to wire up my own 5V regulator like I've seen all over the place, I get nothing but a black screen.

If I wire it up this way(ground going to where previous 5V regulator grounded or else the mainboard exposed ground) the game starts up, but there's no audio.

I'm pulling my hair here. Anyone have any idea what I need to do to make this work? Again, the SNES works fine if powered via the usual AC adapter route, but that thing is monstrous and a power hog.

 

[realyst]

Is this somehow because, in this initial testing, I'm still using the multi-av cable instead of wiring things directly to the ICs?

 

[realyst]

yup, that's exactly what was up: the multi-AV cable is grounded differently, if the connection is done straight to the sound chip, it works.