My Macintosh 512K turns on with two pops ~ not a normal startup chime. After booting up, the floppy drive screen will be displayed, and some vertical lines will appear on the screen. Will change, has anyone encountered the same situation and solved it? This vertical line did not appear yesterday, but it appears today. I plugged it in with a plus logic board, and it didn't happen. The monitor and power strip should all be fine.