I'm not able to obtain an adapter from local markets for vga to composite video output. Found a circuit [VGA to composite circuit. Does it work?] 
that claims to work. I didn't had a vga cable so I inserted jumpers into the port and created the circuit in breadboard then to rca composite cable. I found flickering screen when connected to tv but not a greyscale output of my screen, it doesn't detect source.
Why didn't it work? Is it because I must use vga cable instead of jumpers? How to make it work? I also found active adapters that takes external power source.[https://www.amazon.com/StarTech-com-Resolution-Composite-S-Video-Converter/dp/B001NXDQEK] 
Do I need one of them?
(I have an old crt samsung tv that has video, audio & rf input ports only that I want to use as a external display for my laptop
whose lcd screen is damaged.)
Best Answer
No, in general a simple passive cable does not work. You'd have to use some kind of tool to force the VGA output to generate a compatible 15kHz signal. Even if you can manage that, the picture will have low resolution and it will be black and white. You would need an active converter.