SNES Glitching on Startup

I have a number of Super Nintendos (all SHVC-CPU-01 with the independent sound board) that I'm trying to troubleshoot right now, but one's giving me a particularly hard time. When turned on it acts like my other systems (the TV detects an input, but I get no sound or video). However with this particular system if I run Super Mario World, I'll get the 'Nintendo Presents' graphic flash on screen for half a second, along with a distorted sound that replaces the jingle. Both quickly vanish and the system will resume its non-functionality. It only seems to be with SMW that I'm getting anything to show at all, but I'm not certain of what it could be.

So far I've swapped out the connector and sound board, as well as reflowed the solder on the chips and the pins on the underside that connect the 62-pin connector to the board, without any changes to the symptoms. Part of me thinks its either an issue with one of the PPUs or the CPU, the latter of which I have no replacement parts for (I suspect all of my other systems have bad CPUs, and I can't find anywhere to buy more). I also want to be more certain before I start swapping chips, since I've only ever done replacements for in-board chips (my terminology may be incorrect, but I think they're also called IC chips).

I have a picture of the board, but I dont see any outstanding irregularities: