I enjoy watching retro TV on a retro TV set from the 60's. I connect a DVD player to the TV via an RF modulator. This works great except when playing two older DVD sets which are about nine years old. When playing these, the picture is intermittently jittery and fine horizontal lines appear on and off at the top of the screen. Thinking the player was at fault, I tried connecting a new Blu-ray player instead and experienced similar effects. Could the discs have deteriorated somehow? (They are pricey commercial grade DVDs.) Thanks!!