AGBM 01 (AA) Build Test Order

This is the order I would recommend building the AGBM-01. I also highly suggest checking the circuit as you go. This will make troubleshooting MUCH EASIER! If you ask me why your AGBM is not working, my very first question will be "did you follow the build guide?" If the answer is no, I will direct you here (hello and welcome to anyone directed here in this manner).

Recommended equipment:

• Multimeter
• Power source (greater than 2V... like 2x AA batteries)
  • If you put the board in a GBA shell with the battery tabs soldered in, you can put the batteries in this way, though it might be difficult/not possible to do some tests.
  • Beware of the AA battery holders - the last one I purchased had a poor connection to one side of one of the AA batteries, and it was making testing work intermittently. You can certainly use them, just be wary they might have poor connections. You should be ok for the early test steps, it generally only should be a potential issue later on when the screen kit is plugged in.

Notes:

• For the purposes of testing voltages, BT- is the same as GND, so you can use it as an easy test point for GND.
• Remember to disconnect the power from the board while you're soldering! You can blow a fuse if you don't.
• For each step, if you encounter problems, the very first troubleshooting things you should do is check your soldering and check component orientations (if it has an orientation). Also, make sure you actually put all of the marked parts on the board.
• If you have success on one step, but after the next step you encounter issues, then you can be fairly confident it was one of the new parts you put on (or failed to put on properly) that's the culprit.

Step 0: Protect the Button Contacts

Before starting, I recommend taping off the eight contacts for the D-pad, A, B, Start, and Select button contacts. Use kapton tape to keep solder off of the pads. (This isn't extremely necessary if you are adding tactile buttons instead, but still.)

Step 1: Input Voltage Set-up

First step is to get the input voltage and undervolt shutoff circuit set up.

I recommend doing front side first, then back side parts.

Front side parts:

• C1
• D1
• F1
• PTC1
• Q3
• R9, R11, R12, R16, R17
• U3

Back side parts:

• D2
• Q1, Q10
• R15, R24
• SW1

Test 1: Checking Undervolt Lockout

If you have a multimeter, you might want to test this out just to make sure all the parts were correct (I have accidentally switched Q1 and Q3 more times than I care to admit)

• Apply power to the BT terminals with SW1 off. Check these voltages:
  • VCC to GND: input voltage
  • SW to GND: 0V
• Turn switch on, check this voltage:
  • SW to GND: input voltage
• Momentarily short circuit EN to GND without turning the switch off. Check this voltage:
  • EN to GND: 0V

If EN doesn't drop to 0V and stay there after you remove the short, make sure you're actually shorting it with a good connection. If it still doesn't work, then at least you only have a few parts to check out. If you don't put the correct parts on for Q1 or Q3, then it won't work. Some 2N3904 and 2N3906 chips come with different pinouts than others, so make sure you purchased the correct ones. If you have your own, check the datasheets.

Step 2: Main Converter

This will generate the 3.3V supply, though it will be gated to the CPU until the 2.5V is generated afterwards. The converter is also responsible for the 5V generation, which is also turned on after the 2.5V rail is up.

For soldering the main converter chip, U5, I usually use a hot plate, but hot air can also be used. Do not attempt to hand solder this part - it will not work. This is not a challenge. You cannot do it and safely attach it to the board.

NOTE: Reminder to tape off the button contacts with kapton tape if using a hot plate.

Back side parts:

• C21, C37, C40, C41, C42
• L1, L2
• R13, R21, R22, R23, R55
• U5

Test 2: VOUT3 Generation

Turn the switch on and make sure VOUT3 to GND measures 3.3V. If it doesn't, then you PROBABLY have a problem with U5. It is a tricky part to solder correctly. Use lots of flux!

Step 3: VDD2 Generation

This step will generate the 2.5V supply and allow the 3.3V to connect to the CPU. The 5V supply will also be generated.

Back side parts:

• C2, C22, C60, C80
• R8
• U8, U18

Test 3: Power Rails

Connect the power, turn the power switch on, and check the following voltages:

• VDD2 to GND: 2.5V
• VDD3 to GND: 3.3V
• VOUT5 to GND: 5V

Step 4: Power LEDs

Now we will add the power LEDs! If you haven't been checking the voltages with a multimeter, this step will serve as a check on your work so far. If the LEDs turn on, great! If they don't... good luck figuring out why.

Front side parts:

• DL1, DL2
• Q9
• R3, R4, R18
• U10

Back side parts:

• C12, C10, C44, C68, C72
• R10, R25, R58, R63, R64, R65, R66
• Q5
• U14, U17

Test 4: Power LEDs

Check to make sure the power LED turns on, either green or red. If you have the ability to change the input voltage, try sweeping it from 2V to 3V to see if the color changes. It should go from green to red at 2.3V (when voltage is dropping) and should start blinking once it gets below 2.1V.

As a final test, short EN to GND to make sure power/LEDs shut off until the power switch is cycled.

Step 5: Final Power Staging

These parts manage the 5V supply going to the screen, and the gating to the audio supply voltage.

Top side parts:

• C23, C59
• U4

Bottom side parts:

• C61
• R7
• U11

Test 5: Verify Gated 5V Supplies

Apply power, turn on the power switch, and measure these voltages:

• VDD5 to GND: 5V
• VAUD to GND: 2.5V

Note: initial revisions of the board (May of '26) have the VAUD test point labelled as "BATT"

Step 6a: LCD Connector

This is just to make assembly easier. It won't be needed yet. As such, there's not really a test for it. Just put it on while the space is empty!

Back side parts:

• P2
• R67
• VR1

Step 6b: CPU and RAM

Alright, this is what it's all been leading up to. If you've made it this far, the CPU and RAM shouldn't be all too hard. Just be careful and take your time.

For this step, I would probably use a hot plate for all the components (depending on the package style, I might leave off the crystal for hand soldering later just for convenience), and then go over the CPU and RAM pins with a soldering iron using a drag soldering technique.

Front side parts:

• C3, C4, C5, C6, C8, C15, C16, C30, C34, C45, C46, C47, C48, C49, C50, C51, C52, C53
• EM7
• R1, R5, R26, R29, R36, R41
• U1, U2
• X1

Test 6b: Screen Test (GBA Mode)

The biggest step so far - plugging in your screen kit and trying it out. It should boot to the GBA splash screen intro. Here are a few things to check if something goes wrong:

• If your power LED turns off, that means something is tripping the undervoltage lockout. That might be because of a short circuit somewhere on the board. First thing to try would be taking your screen kit out and seeing if it still happens, to rule out any screen kit issues.
• Make sure you have all the parts placed on the board up until this point. One example - if you forgot R36, then the screen will remain black when it's turned on.
• Make sure you've put the ribbon cable in the connector the proper way (not upside-down), inserted it in fully, and secured it with the bale. Make sure you also clean out any flux in the connector with isopropyl alcohol, it might be causing poor connection on the ribbon cable.
• Check the soldering on both the CPU and the FFC connector. The connector specifically is usually a point of failure for many (including me).
• If the screen turns on but there's a failure to boot to the splash screen, or the animation looks weird, or the colors are off, then you may have an issue with the RAM connection. Check pins 44-83 on the CPU (the right side pins and the right half of the top pins on the CPU) and all the RAM pins. Even one pin missing solder here can screw it up.
• If the screen turns on, and the GBA splash screen animates as intended, but the entire color tint is off (make sure it's not a touch-sensor-induced color palette swap with your screen kit), then check out pins 84-107 on the CPU and the pins on the FFC connector.
• If you're using an ITA kit, you'll need to adjust VR1 to make the screen look correct.

Test 6c: Screen Test (GBC Mode)

Same as last test, but this time it will boot into GBC mode. This mode has slightly different failure mechanisms than GBA mode, so it's worth running this now to help find errors earlier. In order to boot into GBC mode without the cartridge connector, you need to short circuit the C2 and S1 pins to apply 3.3V to IN35. This only needs to be done when the game first turns on. One thing I've done to activate GBC mode is to short the two points together with my conductive tweezers while I turn power on. Or, if you want to be a cooler person than me, you can solder a short wire - just make sure to get all the solder out of the holes afterwards to make soldering the cartridge connector easier.

Unfortunately, not all errors can be screened for with these two tests - a missing pin here or there might still give you the splash screen, but may still not boot into a game properly. You will have to wait until the step where we add the cartridge connector to truly check if everything is properly soldered. But successfully testing GBC and GBA booting will get you the majority of the way there.

Step 7: Audio

I probably would populate the back side parts with a hotplate first, then hand solder the top side parts.

Back side parts:

• C9, C25, C26, C27, C28, C29, C31, C32, C33, C35, C36, C38, C54, C55, C56
• P3
• R14, R30, R31, R42, R45, R46, R47, R48, R49, R50, R51, R52, R54, R56, R57
• U6, U7, U9
• VR2

Front side parts:

• C24
• CP1, CP2, CP3
• Q6
• R19, R20, R34, R37, R53
• SP1

Test 7: Speaker and Headphone Check

Connect power, turn the switch on, and listen for the start-up noise! That's all there is to it. Test the speaker, then also you probably should plug in headphones to make sure both the left and right audio channels are working.

Step 8a: Cartridge connector components

You should make sure everything is working up until this point! Once you put the cart connector on, some parts get hard to access. There are only parts to add to the top side, other than the cart connector on the back (not pictured, I don't have a 3D model for it).

Front side parts:

• C7
• R2, R6, R38, R39, R40

Back side parts:

• P1

Test 8: Playing a Game

Time for the moment of truth - a full cartridge test. This is where you might discover some problems with your soldering on the CPU/RAM. Depending on the game, if you're missing a connection somewhere or have a solder bridge, the game may act strangely or lock up. I don't know exactly how every game will react, but here's an example I ran into:

I usually use Pokemon Sapphire or FireRed to test with. If I have a connection issue with the RAM or the CPU pins connecting to the RAM (the right side pins and the right half of the top row of pins), sometimes I'll get the Game Boy logo at start-up, but not the "Nintendo" text on the bottom. Then, the copyright information for the game will flash on screen instead of fading in, and then the game locks-up. Reflowing the RAM and CPU solder joints has always fixed this. It might also be worthwhile to reflow the cartridge connector pins on the CPU as well (the bottom row of pins).

Once you've got a game booting, if you have a flash cart, I recommend the 240p test suite ROM and/or Natalie the Nerd's GBA test ROM. To test the buttons, you can remove the kapton tape and use a button membrane to go over each button contact! Or...

Step 8b: Adding Tactile Switches (Optional)

...you can add the tactile buttons. I personally don't like these, but you might.

Front side parts:

• SW4 (x2)
• SW5 (x2)
• SW6 (X4)

Step 9a: The Rest

Last step is to add all the remaining parts. This will add the L/R buttons, link port functionality, and enable sleep mode capabilities (for the few games that use it).

Front side parts:

• C17, C62
• EM3
• SW2, SW3

Back side parts:

• C11, C13, C14, C18, C19, C20, C63, C64, C69, C74, C75, C76, C77, C78
• EM1, EM2
• Q8
• R35, R43, R77
• RA1
• U12

Step 9b: The Rest (Part II, Optional)

Here are the parts for the button combination circuitry that you might not want (but why not? it's cool):

Front side parts (optional):

• C43
• Q2, Q7
• U16
• Z57, Z58

Back side parts (optional):

• C39
• R68
• U15
• Z70, Z71

RST - Soft Reset

If you install the hotkey components and want to be able to soft reset your system, you need to bridge JP1 (labeled as "RST", on the top right back side of the board) with solder to enable the functionality, which is activated by pressing L+R+Start+Up.

The Z Components

If you want L+R+Start+A and L+R+Start+B to replace touch inputs on screen kits, populate the Z components with the designated capacitors. If you want them to act as a regular button input, use the resistors/jumpers specified. See the Feature Configurations page for more info.

Test 9: The Rest

Now that you've finished assembly, you can verify:

• Link cable compatibility
• Hotkeys
• Sleep mode

As mentioned earlier, I recommend the 240p test suite ROM and/or Natalie the Nerd's GBA test ROM. Not many games use the sleep mode functionality; the one I use is the best and clearest-named game on the Game Boy Advance, Super Mario Bros. Advance 4: Super Mario Bros. 3. There's an option for it in the overworld menu.