Here's a simple guide for you to get your Master System console ope and ready for modding!  

Retrobrad has been created and maintained by me - Brad!
This page has been visited times since June 2007

by retrobrad 22 June 2007
  Unscrew the metal shielding and all other screws holding the mainboard down (including the two holding in the cartridge connector).  
  First things first, flip your console upside down and unscrew the six screws as shown in the picture. Once they're unscrewed, turn the console back the right way up and remove the top cover.  
  Once it's all unscrewed you can remove the mainboard from the housing. Then just unscrew the big metal heatsink and your ready for modding!