SOURCE:
https://blog.gg8.se/wordpress/2009/07/22/testing-gameboy-input-voltage-ranges/
https://archive.fo/4qXoQ
https://web.archive.org/web/20200527071249/https://blog.gg8.se/wordpress/2009/07/22/testing-gameboy-input-voltage-ranges/
########################################
##### Official GameBoy Power Supply Info
########################################
** Center Tip Negative

** Regular Alkaline AA batteries are rated to provide a 
nominal 1.5 volts and 1800-2400 milli-amperes per hour 
(1A = 1,000mA) depending on the energy drain of the powered 
device.

** 6 Volt
** 0.7 Watts
** 116.66 mA
** Original power adapter : 6V (unregulated) 100mA max

########################################
##### Official Battery Pack Info #######
########################################
* 4.8 Volt
* 150 mA
* 2400mAh = 20.57hrs ( 2400mAh / 116.66mA)

* A 470uf or larger decoupling capacitor is added across 5V 
and GND on the power regulator pcb.  This helps eliminate any 
buzzing or hum from the speaker (The backlight will make Game 
Boys noisy if this is not done. You can't hear the Game Boys 
you are buying so watch out!). Game Boy is tested for audio 
quality using an AC power supply which will produce more 
distortion/line noise than DC batteries. I want these to pass 
my testing under the worst conditions. I will swap the main 
board if needed. 

########################################
##### GameBoy Minimal operating Voltage 
########################################
Test Data
------------------------------------------------------------
Vin (V) 	IIn (A) 	Vout (V) 	DC/DC control RMS/f 
------------------------------------------------------------
1.5 	0.15 	4.79 	~2.1V 	       
* Notes: Prone to crash, no sound, DC/DC buzz on startup

2.0 	0.12 	4.82 	~2.4V 	       
* Notes: No sound

2.5 	0.11 	4.84 	~2.7V          
* Notes: Display will lose data when playing sound

3.0 	0.05 	4.87 	~3.0V/~260kHz  
* Notes: Appears to work normally, possibly a bit glitchy/unstable

3.5 	0.06 	4.86 	~3.2V 	 

4.0 	0.05 	4.87 	~3.5V/~300kHz  
* Notes: Fully normal operation

5.0 	0.05 	4.88 	~3.5V/~320kHz 
 
6.0 	0.04 	4.89 	~3.6V/~390kHz

########################################
#####  Backlight #######################
########################################
* Pololu 5V Step-Up/Step-Down Voltage Regulator S7V7F5 
	* Use for DMG GB
	* This is the one I used for my GB. It works great 
	  so far. I'm currently usinf it for the back light,
	  but I would like to buy another & replace the stock
	  GB Regulator and compare the power draw.
			
* Pololu 5V Step-Up Voltage Regulator U1V10F5 
	* Use this one for the gb pocket
			
* "DC-DC 1.8V 2.5V 3V 3.3V 3.7V To 5V step up power voltage 
boost converter board"
	* If you copy/paste the entire name in quotes above 
	into Ebay, You will see a bunch of generic regulators. 
	Remember, You get what you pay for.
	* I haven't tried any of these, so do your own research.

* 500 ohm potentiometer (Or Slider)
	* This is the type of pot used for the backlight.
	* Completely optional.
	
########################################
##### Connecting the Backlight and pot #
to your GB #############################
######################################## 

* Connect + of backlight to 500ohm pot
* connect - of backlight to gnd of regulator

* Connect pot to voltage of regulator

* Connect gnd of regulator to GB-DMG 
* Connect Vin of regulator to + of GB-DMG