messing up input and output

I have just purchased a panasonic 26 inch Tv and a panasonic dvdr.  They work great. I wanted to also connect my old dvdr as a AV2 external link as I like it (its easy to use) Unfortunately after 2 days the picture became disrupted. I took it off and connected the TV input scart lead to my old tv input scart socket. The picture was disrupted.  By chance I decided to put the scart lead into the vcr/sat scart socket and there was the picture etc but with no sound.  I have definitely mixed up the signals.  I want if possible to keep it as the AV2.  If this is not possible I want to record my dvds onto my new machine.  My old machine was very cheap and the 'make compatible' system it has does not work very well so I cannot play my dvds recorded on it on other machines.  Can someone explain in laymans terms how signals go from one scart to another so I can try and understand what is going on.  Thanks