I realized I might have messed up.
There's a ceramic capacitor next to the big boy 400v electrolytic that I accidentally bent flat wile reassembling a metal bracket on the frame (it got caught underneath without me realizing). I put it back up and it doesn't look damaged or loose, although I can't imagine getting flattened did it any good.
Could this be the cause of the "singing"? I'm not knowledgeable enough to understand the schematics and its role, but I've attached it here in case anyone smarter than me wants to take a look. C913 is the ceramic and C908 is the big electrolytic. Any help is as always immensely appreciated
PCB Pattern
https://postimg.cc/NLKYhPG8
PCB Schematics
https://postimg.cc/JGjfmffX
Photo
https://postimg.cc/0zxLNtvB