Playing Game Boy Color Games in an Original DMG Shell

I recently got really interested in Game Boy console modding. I started watching The Retro Future on Youtube and saw a bunch of his videos of refurbishing and modifying old Game Boys, and I became intrigued. My first Nintendo console of my own was my purple Game Boy Color (that I annoyingly can’t locate), and I never had an original Game Boy, but I’ve always had an affinity for the original design (the “DMG” model).

I decided that, since I never had a DMG, I should finally buy a crappy one and fix it up. It seemed like a fun project! So I bought two DMGs (that were supposedly “dead” but really weren’t). I figured instead of making a bunch of smaller modded consoles, I should just fix up one console without any modifications for display purposes, and then make one really nice console with all the bells and whistles that I’d like – the main features being an IPS screen and rechargeable batteries. But the more I started adding up costs and thinking about the games I wanted to play, the more I realized that there were a TON of GBC games that I’d really like to play on a nice IPS screen. But the GBC’s form factor isn’t my favorite – mostly due to my large hands. And I didn’t want to have a modded DMG and a modded GBC, especially if the GBC could do everything the DMG could.

So… what if I could fit a GBC innards inside a DMG case? After taking them apart, that was an immediate “no.” For starters, the buttons are in different locations. There is just one large PCB inside the GBC, as compared to the DMG’s two separate boards that slot nicely into the plastic. The biggest problem was the cartridge connector wouldn’t be accessible without some heavy modifications and carefully removing it from the GBC’s board. And even then, if I could do that efficiently, I’d have to figure out how to get the buttons to work, and the battery compartment was also in the way of the main PCB, and it just wasn’t an ideal set up.

The next generation up was the Game Boy Advance. I could just modify a GBA, or a GBA SP, but I really hate how the non-GBA games stick out of the console. I get it, it’s kind of a necessary thing, but I just don’t like the look at all. Then, I stumbled across a few posts from people who put a Game Boy Advance SP inside a DMG case. The original GBA board was too weirdly shaped to fit inside the DMG case, but the SP? It was a comparably smaller square. With some modifications, like removing the surface mounted cartridge connector (an easier sell than removing the through-hole GBC connector) people have been able to get their SP inside the DMG case and have a fully functional GBA. This became my new goal.

So, looking through a lot of different projects, it seems that there are many different ways people have done this in the past. I saw many people mod the outside shell to accommodate the actual GBA functionality into the console. That was a non-starter for me. Firstly, I don’t think I’m good enough at modding cases to make them look nice. I try to do as minimal outside work on these kinds of things as possible. Plus, it kind of messes up the original aesthetic for me. I’ll make a separate modded GBA later for those games if I really want it. You can make some really slick GBAs, and those consoles are comparably cheap and abundant anyway.

So I will effectively be making a DMG that can play GBC games.

So, the screen size will stay smaller, and I won’t be adding any buttons onto the console. As for the battery mods, there was one I saw that put a USB port in the back of the DMG battery cover, and some that used one of the DMG’s ports to add a USB port, but I really didn’t like how that looked. So as I paged through pictures of others’ mods, and looking at a lot of various Game Boy schematics, I started to get an idea of what I had to do to get effectively a Game Boy Color into a DMG case with as few external modifications as possible.

For reference, here’s the schematic for the SP, and here’s one for the DMG – though, I measured the volume wheel and it’s a 10kΩ, not a 1kΩ. Still good for reference. Until I take pictures of my own, I’ll be using pictures from this forum thread and this Youtube video for reference.

So here’s my battle plan.

Preparing the SP Motherboard

The first thing I’ll have to take care of is the SP motherboard. The quick and dirty explanation is that I’m removing all of the larger parts from the board to either get rid of entirely, or to repurpose elsewhere.

Cartridge Connector

The cartridge connector is the most important part of the SP motherboard that I’ll need to save. It’s also the most difficult to remove. Because it is surface mount, I thought about using a heat gun to remove the connector, but there are a lot of pads and a lot of sensitive parts nearby that I don’t want to desolder accidentally. I found a video of someone taking it off by using a Dremel to cut the pins, and then desoldered the leftover pin clippings left on the pads. There is plenty of room left on the connector pins to solder new wires to, and this minimizes the heat going to the SP motherboard. So I think this way is probably the safest.

Game Boy Mode Switch

Near the cartridge slot, there’s a switch that is actuated when a Game Boy or Game Boy Color cartridge is inserted into the SP’s cartridge slot. GBA games don’t hit this switch. This switch will tell the SP which mode to run in. Interestingly enough, GB and GBC games run at 5V, whereas GBA games run at 3.3V. So this switch will effectively change the operating voltage of the cartridge slot (and EXT connector), just depending on which game you have inserted. Neat!

Because I’ll only be using this for GB or GBC games, I’ll remove the switch and hard wire it to permanently be in 5V mode. Very easy to do.

Other Ports and Switches

As for the rest of the parts, I’ll simply be removing them for the time being. I’ll go into more detail later on of how exactly I’ll be using them.

  • The power switch and volume slider will be wired to their DMG counterparts.
  • The EXT port (for link cables) will be simply wired to a DMG model EXT port.
  • The battery contact will be directly wired to my new battery and battery charger board.
  • The charging port (with audio out as well) will only be wired to the audio jack.
  • The L and R buttons will be removed completely!

Overview of the DMG

Here I will break down each of the features of the DMG, and what I plan to do with them. For this, I will need the donor SP motherboard described above, as well a donor DMG to use for various parts. The ones I’m using for this mod are both damaged in some manner (that I’ll have to compensate for in some cases, as you’ll see).

Cartridge Connector

I haven’t totally decided yet if I’m going to use the SP or the DMG cartridge connector. I’ll have to make this decision when I start trying to put it together. If I go the route with the SP connector, I’ll have to glue it in place, whereas the DMG will sit nicely on the posts and screw in, but give me less space to work with. I’ll have to see how tight everything is.

Screen

Because I will be using the innards of an SP in this build, I am going to use a GBA SP IPS screen mod to connect to the motherboard. The SP screen is wider than the DMG’s case will physically allow, so I will have to shave off some of the standoffs to get it to fit properly. Not a big deal, I’ve seen people do this before. I just need to make sure it is centered properly. I’ll need to make sure the screen lens is removed, so that I can have it flush against the front case. I’ll hold it in with some electrical tape, or some other method.

The external screen lens will be replaced with a glass one, for maximum durability.

Now, most GBA SP IPS screens come with the lens already attached, which is redundant for me since I’ll also have the DMG lens. But Retro Game Repair Shop offers the screen separately, so I can get one and buy a ribbon cable so I don’t have to risk damaging the screen removing the lens myself. I’ve heard it’s not easy to get them off without damaging something.

SP Motherboard

The stripped down SP motherboard will sit behind the screen, in the top half of the DMG shell. Placing it sideways seems to fit best, plus, the standoffs are already shaved down so the screen can take advantage of that too. Apparently, some people have had to cut notches into the motherboard to make it fit. I’ll see how it is when I get to that point.

Power Switch

The DMG power switch is straightforward to connect to the SP motherboard. Just wire it where the old switch used to be. Done! Securing it to the case, on the other hand, will require some thought. Gluing it seems to be the easiest option. Luckily, the plastic piece that actually moves the switch gives us some room to work with.

Power LED

There are some modifications out there that completely omit the power LED from the build. I can understand this – the SP’s screen overlaps where the LED is supposed to go. Quite annoying, actually. In order to get the screen to fit flush against the case, you have to shave off the plastic ring around where the LED sits.

But, I really want that LED in there. It just won’t feel right without it. So my plan is to use a surface mount LED in the hole, and drill out some of the case where the screen lens will be covering, and route wires to the LED through there. The plastic is about 2 mm thick. You can easily get a small surface mount LED and thin gauge wires to fit. The opaque screen lens should block everything out that you shouldn’t see to make it look like the original DMG indicator. My planned cut is below in red. I also plan to have a two-LED package in there – one red for when it’s operating normally, and an amber LED for indicating charging.

A, B, Start, Select, and D-pad

Because the SP obviously doesn’t map the buttons to the proper locations, I need to use another circuit board separate from the SP for the button inputs. You could cut up an original DMG board for this, but instead of destroying the screen and button DMG PCB, I’m opting to use a custom-designed DMG compatible replacement that I found on this forum. Then all I will have to do is wire these DMG buttons in parallel with the SP’s buttons.

Headphones, Speaker, and Volume Control

The SP’s speaker is smaller than the DMG’s, but I believe they are the same impedance, so I can easily swap out the SP speaker for the DMG one. No issues here.

As for the headphone jack, you might recall that the SP didn’t have a headphone jack. Instead, it output audio through the charging port. I think all I have to do is pull the left and right audio channels from the charge port and wire them up to the headphone jack on the DMG audio board. I’ll test this out before actually mounting anything.

Now, for the fun part. The volume wheel (or slider for the SP) is a simple potentiometer, that is, a variable resistance. Unfortunately, the DMG wheel is a 10kΩ potentiometer, whereas the SP’s volume slider is 30kΩ. Fortunately, the potentiometer on the SP is just used in a voltage divider circuit. It’s a 30kΩ pot in series with a 3kΩ resistor. So, if we just change the volume slider to the 10kΩ pot, we can change the 3kΩ to a 1kΩ resistor and the function should be the same.

Battery and Battery Charger

The battery has the most electrical modifications necessary for this mod. My SP motherboard has a non-working charging circuit, but the whole system still works if you give it a charged battery. On top of this, another consideration is that I’d really like to not have to use the original SP connector or put a USB port anywhere in the case to charge up the battery. Neither fits nicely anywhere on the case without sacrificing something else, and like I said at the outset, I am trying to modify the case as little as possible, so no new holes!

There is a DC jack, though. So I will be using this jack to charge the battery. Originally, I was going to design a battery charger circuit board myself, but the cost of doing this is a bit high. So I instead opted to use Adafruit’s affordable LiPo battery charger, along with one of their LiPo batteries (with built in protection). I will not be using the USB port on the charger, just wiring directly to the 5V input instead.

But! The DMG charger outputs 6V DC, not 5V. If you look at the datasheet for the MCP73831, the maximum supply voltage it can handle is 6V. So… we might be able to get away with connecting to the DC jack directly. But that’s way too close for comfort – I imagine the charger might output higher than 6V depending on the outlet you use, as I suspect it’s an unregulated supply. In order to handle this, I will be using a buck converter to step down the voltage and keep it at 5V maximum. Again, my original plan was to make this all on one circuit board, but these “eBoot Mini” converters on Amazon come out to only $1.50 each! And they have a tiny footprint too. You can’t beat that.

So in summary, I will be using the power from the DC jack on the DMG, at 6V, through a buck converter to regulate at 5V. This 5V will pass to the battery charger, to the LiPo battery, which will be connected directly to the battery terminals on the SP motherboard. This way I can offload charging from the SP to these external boards and effectively replace the damaged charge circuit on the SP.

EXT Port

The DMG model’s EXT port is a different size than the Game Boy Pocket, Color, and Advance consoles. They’re still compatible with the correct link cable. The SP’s EXT port is a different size from the DMG, but the pinout is still the same. In fact, when the SP is in GBC mode (which mine will be hard wired into) the output of the link port is 5V, whereas if it is in GBA mode, it’s 3.3V. Because the protocol is the same, and it will be outputting 5V onto the EXT port, you can simply wire the port to the correct pins on the SP motherboard. Holding the port in place will be annoying… I’m thinking I might try to cut off a piece of the original DMG PCB that has a hole for mounting, and glue it on to secure it.

Contrast Wheel/Brightness Control

Here’s where the plan hits a road bump. Every other external component (that isn’t the buttons or the headphone jack) is located on the back side shell. The contrast wheel is located on the top shell. The reason is the contrast wheel was part of the top PCB on the DMG that had the screen on it. So why is this a problem?

Because the stupid SP motherboard is sitting here, and the contrast wheel is so large that it’ll interfere with the board. There actually IS a contrast potentiometer on the GBA models, but it’s hidden inside the console, not normally accessible by the user. I thought about wiring the contrast wheel to that instead, but I never needed it before, so it’d be kind of excessive to include. Besides, I’m missing something else that’s a bit more useful – the brightness button.

So this is what I plan to do. There are small push buttons that come in a rectangular package. The buttons are pretty low profile, to be honest, and they don’t actually fit in the contrast wheel slot. But if I shave off the little extra plastic on the contrast wheel, I can slot them in. I also have a 3D printer at my disposal, so I might print a button cover to fit exactly in the contrast slot, and place the real button behind it. This is the most elegant solution I could think of that didn’t involve cutting a hole in the DMG case.

So, in all, I should be able to make a fully functional Game Boy Color, with a nice bright screen and rechargeable battery, in a (nearly) unmodified DMG case.

Development Notes

Here I’ll write down miscellaneous thoughts and progress as I go, before a full formal write-up. This is to help me not forget things as well, because this project is going to take place over the span of probably a month or two after gathering all the parts, at least. This will be all over the place – it’s more for my benefit than yours, but feel free to read through it.

04/03/2021

Screen

After multiple polls on social media to help me decide the color of this thing, I’ve picked a teal DMG case to use. It’s very nice! I’ve begun cutting up some parts to start fitting things in. I started by checking the screen alignment. I cut some of the mounting posts so I can fit the screen in centered, but found a problem.

I neglected to take into account the side bar of non-screen space. So I had to cut farther into the right posts, and actually had to completely remove one. In order to keep the screen centered, I designed and printed a bracket with my 3D printer, that fits on top of the remaining posts. I also added a piece that sticks up, so that I can glue the post back on, to screw into eventually (where the top right post would be in the picture below). I could probably just 3D print the post but I’m not sure if those posts are pre-tapped or not. I’m not really in the mood to find out!

This holds the screen in nicely. But I had to use a dremel to cut into the bottom right post as well. The two left posts have some plastic routed out from the initial screen placement, but found that I didn’t actually need to cut them (yet). The SP motherboard might require some more adjustments.

There’s a little blank spot in the bracket on the bottom right, that’s for any wires from the power LED to come back through. Still messing around with that idea.

I plan to use this bracket to hold up the brightness push-button as well. So this bracket isn’t the final revision. Also, after I cut up the DMG PCB, I might make some mounting points where the switches/dials can rest for easy gluing. I’m not sure yet, still have to prepare that. But this bracket provides an opportunity to get some nice mounting spots, instead of gluing everything to the side of the shell or something.

Battery

I cut a portion of the DMG shell so that the 2000 mAh battery will fit inside the battery compartment. I also plan to have the charger and buck converter resting in here as well. I ordered kapton tape so I can wrap all the exposed metal on the boards, to prevent short circuits. This picture only shows the charger, but in the end all that will be coming into this battery compartment are the two wires from the DC jack, and then two wires going out to the SP motherboard.

I tried removing the USB connector on the battery charger board, but that requires too much heat so I gave up, to prevent damaging it. It’s not that much space anyway.

I could probably start getting the battery and charger wired up to the SP to make testing things easier, that might be my next step. Right now I’m just holding the original battery in myself while I test.

Preparing the DMG/SP motherboards

Before I start cutting everything up, I need to make sure all the original boards work as intended. I already know the battery charger doesn’t work on the SP, which is why I’m using the external charging board, but I need to make sure everything else works fine, like the link ports, audio, and various potentiometers. I also need to determine if I can just grab the L and R channels on the SP charging/audio port and put them to an audio jack. I’m hoping it’s that easy, but I’m kind of doubting it. Need to check the schematics more.

The DMG’s headphone jack works. But the external audio doesn’t. I don’t know if that means the motherboard’s audio is broken, the speaker is bad, or if the potentiometer is. I need to check. If it’s the motherboard’s problem, I don’t care, I just need the potentiometer to work. I bought another speaker for like a dollar anyway, so I don’t care if it’s the speaker either.

I ordered a link cable to double check that the ports are working ok. I don’t think I have a link cable for the GBA unfortunately, so once I verify the DMG port connections are fine, then I’ll cut it off and wire it to the SP motherboard and test it there, instead of using the original link port on the SP.

I also need to do a deep clean of the DMG parts. The one I have to use as a donor for the project is quite dirty.

04/10/2021

  • Removed L, R, and ports (tested ports)
  • Button PCB wired up
  • GBC mode permanent
  • cut DMG PCB
  • adjusted bracket
  • plans for cutting SP board (and new LED location)
  • new power switch wiring
  • new potentiometer wiring

4 thoughts on “Playing Game Boy Color Games in an Original DMG Shell

  1. Keen to see how this goes – also wanted to work out a IPS GBC compatible DMG but don’t have enough spare parts around here to test fitments.

    With all these new IPS screen mods figured I’d just use a GBC kit in the DMG and route things around to fit but hadn’t considered the size of the battery compartment getting in the way… Wonder if there’s a way to remove the bottom half of the GBC board? I know there’s secondary points on the top half of the board that map to the buttons but not sure about removing all the audio circuits and rebuilding them – SP seems like an easier time in hindsight.

    If you can get the display showing up in the right spot within the gameboy lens this will likely be an awesome mod to complete

    Like

    • I had looked for places to cut the GBC board, but there are traces for the audio and DC jack, as well as a little separate board that has a switching power supply on it (boosts the AA voltage up to 5V). I didn’t feel like figuring out where to put those or where to find places to grab the traces on the top half.

      Lining up the screen will be the most important part for me haha, if it’s not perfect it’ll bother me forever.

      Like

      • Yeah totally get that – I’ve seen someone fit a GBC into a gameboy pocket – definitely needs a few trace jumps here and there so I can kind of see how it might work? (https://www.youtube.com/watch?v=AYPK6QRk2E)
        If I end up finding a cheap GBC I’ll do some testing an leave a note here, definitely I’m expecting to re-use the switching power supply it has because of the weird voltages used in a few places though I’m sure that’s manageable other ways as well.
        Audio jack was just going to replace the whole audio circuit – lots of ‘Prosound’ mods out there that bypass the circuit entirely so shouldn’t be too bad.

        Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s