20 YR. OLD DIRECT VIEW UNIT. 8 MONTHS AGO WHEN FIRST TURNED ON VERTICAL LINES APPEARED ON TOP 1" OF SCREEN, LEFT AFTER 10-15 MIN OF "WARM UP". NOW LINES ARE ON 1/2 THE SCREEN AND TAKES ABOUT 40 MIN OF WARM UP. IS IT TIME TO GET A NEW SET ? WHAT DOES THIS INDICATE ? I'VE NOTICED THE OLDER SETS ARE JUST ABOUT IMPOSSIBLE TO FIND PARTS.. ANY ADVICE APPRECIATED.. MIKE