Follow up to the notice below, I was right, it was the Sony display.

I touched up the diodes in the battery circuit on the Supermicro board, thoroughly cleaned it up, and powered it on. The display happened to glitch up at that time, so instead of rebooting the system, I turned the display off and back on again... and the display was normal again.

I have two of these 20+ year old displays, and this panel is the first of the two... and it happens to have rare display issues, but the panel has no dying pixels, and the bezel is fine. It also has a matching back. The second one has (barely noticeable) dying pixels, but it functions perfectly otherwise... but it has a dent in the top right corner. It also has no matching back.

I'm going to swap the power board and Tcon from the second one into the first one and retire the other display. Dad has the second one (which replaced the first), so it goes back to him after this.

I'll have to retrieve another display for the retro setup, it seems.

http://cwcyrix.nsupdate.info/gnu-social/public/notice/232