Here is a power supply circuit for sega game gear for the additional collection of your circuit. For a more complete explanation can be found on the website http://hardware.speccy.org.
Note: The value of the supplies provided by this sega power supply circuit, only take from the game gear and can not measure the value of the original circuit.
MB3775 is a switching regulator with two independent outputs. With one of the +35 v output for backlighting on Game Gear. With others, +5 v output is needed to feed the chip. Reference signal which makes MB3775 (1.25V) is also used but do not know its function.
The diode D1 (SM label 3F), which prevents current to pass if we get a polarized power in reverse.