Ok so finally I put in the audio board again, and it seemed to work, I got audio for about 10 minutes, then there were some crackling noise and sound dissappeared. Perhaps stupidly, I left it on to fix some video settings (got a new TV so was pretty eager…) and after about an hour, the unit froze. Turned power off/on, then the screen was lit but blank (similar to previous problem), but additionally, the D1 and D2 LEDs were continuously on (strong red for D1, weak green for D2).
Once again, I removed the board and regrounded pads, and carefully resoldered the crystal pin. However, the problem persists…! Did I finally really break something??
Thanks again in advance for any input on this!