well have you got a screwdriver set ? if so you need them to be able to get into the PS2... once you have your equipment heres what you do
First off Disconnect all power and A/V cords from your PS2. Ensure all devices including memory cards, controllers, compact discs and/or DVDÂ’s are removed from the system.
Turn your PS2 upside down and remove all eight screw caps (4 rubber and 4 plastic). These caps cover the PS2 assembly screws. Pry the caps off gently using a small FLAT head screw driver. Note: Four of the eight case screws are 2 1/2" in length, and all screws must be re-used in their appropriate holes only.
You can use a Kitchen Knife to take those Plastic Caps off and the rubber ones
After you have removed all 8 of the case screws, you will need to turn the PS2 right-side-up and remove the top cover. Lift the top cover of the PS2 case up and away from the exposed controller ports and drive tray on the front of the console. Important: The top of the PS2 is attached to the bottom via a thin ribbon cable which connects to the Reset/Eject switch. Ensure not to damage or remove this ribbon cable when removing the PS2 top.
The next step is to remove the Reset/Eject switch assembly from the top cover of the PS2. Gently pull the plastic switch assembly free from the PS2 top cover, ensuring not to damage the thin ribbon cable.
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there is a picture that i added... this is the ribbon cable that might of untached whilst moving it or something this can stop your PS2 from powering on.... if its not that then make sure the Fuse hasnt blown inside the plug... ( im sure the Ribbon Cable Shown in the Picture is just a simple slot in ) atleast if i can remember
NOTE: If You going inside the PS2 there will be a sticker at the back of the console its about Guarantee i think if you remove that ( which is what you need to do to get inside the PS2 ) your Guarantee is no longer with the PS2 as they might think you have done something inside the PS2 most sellers look for this problem
Good Luck