It's common for the Sega Game Gear to fail. Common failures include white screen or no screen as well as low to no sound coming out of the speaker. This is caused because the onboard capacitors have failed and need to be replaced. 

A comprehensive repair includes the following:

• remove all the old electrolytic capacitors
  
• clean / restore the capacitor landings
• fix any broken traces / vias 
• electrolytic capacitors will be replaced by high quality Japanese brand (Nichicon, Panasonic, Rubycon, ...)
• (optional) install a glass LCD screen in place of the scratched up old plastic one
  
• test the system to make sure 100% operational

NOTE(S):

• On rare occasions the Sega Game Gear's LCD fails and can not be fixed (one or more of the 3 LCD drivers fail resulting in sections of the screen looking darker than the rest)  We can't do anything to fix this, but not all hope is lost. Because the main PCB is still working correctly, this system would be a good candidate for a McWill modern LCD upgrade.