No signal from dvd to tv after hookup

I hooked up the dvd player directly to the tv using rca cables from the red/white/yellow dvd out to the tv red/white/yellow tv in. The power on the dvd comes on and its little display screen shows it is working and playing a disk, but the picture on the tv does not change from the cable input. Pressing setup on the dvd displays setup in the dvd window but not on the tv. The tv is tuned to channel 3. The vcr starts playing a tape properly when play is pressed, but the dvd does not. There is no separate input button for the tv, so I assume when you change from cable to vcr or dvd the picture will change accordingly automatically.