If you cleaned the heads with cotton I am not surprised it didn't work. They are probably more clogged now than ever.
Take a 3 hour cassette press play and just let it run. If that doesn't work then take a clean piece of thin cardboard (cereal box, perhaps), dipped in meths or preferably IPA and hold it against the side of the drum assembly while turning the upper drum by hand.
As a last resort play a recorded cassette - be sure to use an old one because it will become damaged - and apply pressure to the point between the two drums over the outside of the tape using a fingernail. When you remove your finger you will know if it has worked. Try 2/3 times. If you have no luck at this point you will need to seek out a professional, unless you know how to replace video heads, check head amplifiers and test lower drums or back tension bands, deck alignment etc.....
Colin, January 2008
