This kit comes with all the capacitors needed to fix your Game Gear power board, as well as the main IC that generates the voltages, plus all 3 power transistors. We have yet to come across a power board that has not been fully repaired with this kit.
Developed under the name "Project Mercury", the Game Gear was the primary competition to the Game Boy, the Atari Lynx and the TurboExpress. It shared much of its hardware with the Master System, and can play Master System games by use of an adapter. Sega positioned the Game Gear, which had a full-color backlit screen with a landscape format, as a technologically superior handheld to the Game Boy.
The Game Gear was notorious for bad capacitors, which means almost no Game Gears exist in the wild that work without repair.
If the normal capacitor replacement fix does not solve your problem, you likely have a bad power board. You can test the output voltage of the power board by supplying it with 9V and testing your output pins get 34V, 9V and 5V outputs. If not, this kit is for you.