Power Regulator Circuit (Game Boy Advance)
The GBA has a single power regulator that generates the 3.3V, 5V, 2.6V (RAM), -15V (LCD), 13V (LCD) voltage rails.
![GBA Power Regulator Schematic GBA Power Regulator Schematic](https://images.archbee.com/9EnOacbhz7Zqgrsars4GT/8QG--JK93uYMXCLiLOfoJ_gba-power-regulator-schematic.png?format=webp)
In short, the power comes in from the battery (through the battery springs, fuse, power switch and current limit resistor R33.
When there is an over-current detected on one of the outputs, the regulator will shut down preventing any power rails outputting power.
If you get a quick flicker of the power LED then off, use a bench power supply to inject 1V into each output rail (test pads labelled VDD2, VDD3, VDD5, VDD13 and VDD-15) and check for excessive current on those outputs.
If you find no shorts, then check the transformer T1 is not internally shorted (top pins 1 and 3 should be shorted together, but not joined to pins 2 or 4. Bottom 4 pins should all be shorted to each other but not to any of the top pins).
If T1 is good, check L1 has continuity.
From a working console when turned on, here are the expected voltages on the regulator.
![GBA Power Regulator GBA Power Regulator](https://images.archbee.com/9EnOacbhz7Zqgrsars4GT/ERxlA-7xwMka72a5wNMzs_gba-power-regulator.png?format=webp)
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