Odd graphics + sound problems with R-Type Leo

[Dewclaw]

I'll preface by saying I know very little about this sort of thing, so apologies if it's a simple/common problem.

I hadn't played my Leo board in ages, probably since I sold my cabinet. When I try to play it the sound is VERY muffled and staticy, and the graphics are also full of static and flashing, sort of like tracking lines on a VCR. The graphics themselves look fine, the picture is just messed up. I'm playing on a Sigma Raijin if that helps diagnose anything. All other boards I've tested work fine.

One strange thing I noticed is that the graphics and sound clear up slightly if I hold down all three buttons on the control panel. What the hell.

[Dewclaw]

Update: I tried it on my Irritating Maze cab since it works with JAMMA too. There were no video problems, but the buzzing and warping sounds were very loud. Maybe it's a capacitor issue? There are about a dozen on the Leo board, none of them look damaged or leaky but I assume they can go bad without being visibly damaged?