Hi, i have an old car audio player and i wish to modify it so that i can use the power supply from my room power socket and listen in my room. But i check the wire, there are red and yellow. Which one i should connect to the +12V?

 

Both if it follows the standard

 

Ahhh if you have a power supply, then the red and the yellow SHOULD be on the positive of the power supply and ground needs ground obviously.
Yellow is constant and red is switched

 

get a cheap computer power supply

 

^^ then use a paper clip and connect the green wire to ground.

 

opss yup i totally forgot to tell you that, you need to take a paper clip or w/e *i use a 14 gauge solid wired with shielding, then i jump the green and black together and just tape it up
and now you have a 12volt source i usually use my powersupply to test my product that i sell b4 i sell them to clients =)