On this page: http://www.biwa.ne.jp/~shamada/fullmac/repairEng.html#WavyDisplay

Check out the sections on "12. Too Bright Monitor with Horizontal Sweep Lines" and "14. Wavy Display, Swaying Back and Forth of the Image"

The display doesn't look wavy, but the "Welcome to Macintosh" dialog box looks pretty distorted...