infernos

Hi guys a have all the gear i need for a car install but im having problems with my screen, it's 7.5" mini-tech m8800 it has a four pin din which feeds power and video/audio red,blue,yellow,white .I guess yellow is composite vid and white is audio red + / blue - so i have made a lead to connect it to a standard 12v / 300ma power indoors before fitting to the car. My problem is that when i run the tv out (s-video with a phono (composite) converter) on the PC to the screen i get a picture but it like 2 pictures overlaid and waving side to side like a signwave and im perplexed as to what is causing it, please help as this is all thats holding my install up i am running the yellow photo (pc end) to the yellow wire on the screen and the shield wire (screen or ground) from the wire to the nexgative of the power supply. what am i doing wrong ,the tv output is also set to NTSC and not PAL? and i believe is running at 60hz.

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