Ps3 wont work on sdtv helpp!?

i had my ps3 hooked up with hdmi on an hdtv flatscreen but im on vacation now and i brought my ps3 and tried to hook it up to a sdtv after i bought the regular cables from radio shack..it doesnt work tho, like its just black and no picture. i read that if you hold the power on down until it beeps twice it will reset the video settings but ive done that a million times and it still wont work. theres no sound or pictures or anything. help please