If your PS2 Slim console malfunctions and you can't turn it on, you can take it to a tech-savvy professional who can diagnose and repair it. To save money, check all the possibilities yourself before turning to the pro. The console may be down because of a problem you can diagnose after taking the outer casing off.
Check the plugs. Even if you plugged them in correctly, the connections at the back of the PS2 can come come loose. Dust may settle among the connections, preventing them from plugging in fully. Remove the connections at the back and spray canned air on the plugs and sockets. After you have cleaned all the connections, plug them all back in as far as they will go. Try to turn on your PS2 Slim.
Remove the outer casing. Using a screwdriver or a sharp knife, disassemble your PS2. (See References for a guide to disassembly.) The power switch may have moved away from the circuit board. Move it back into place and replace the outer casing. Turn on your PS2 Slim.
Check the power supply. Depending on which country you are in, the voltage will differ. There should be a label somewhere beneath the PS2 that says exactly how much voltage it should be receiving. If it isn't getting enough, it simply won't turn on. To fix this, you can buy a voltage converter online. If it was getting too much power, take it to a professional for repair.
Check the motherboard for a short circuit. If the motherboard has shorted out, take it to a professional to replace the motherboard.
If none of these steps works, replace your system.
Switch off your PS2 Slim if you are checking the connections at the back--even if the console does not turn on. If the console turns on while you are fixing it, you run the risk of electrical shock or electrocution.