There's something so wonderfully twisted about dragging aging electronics kicking and screaming into present relevance that fills me with glee. Hardware that was never intended to serve more than a handful of years can suddenly find itself dusted off decades later and torn apart in search of what is often a single minor flaw preserving its retirement. And when the indignant device whirrs, clicks, or dings back into operation, the real work can begin. Enhancements and stylistic touches elevate the "simply working" to an even more useful state with a distinct personality that isn't achievable with stock configurations.

I have more than a few projects like this, but I continually find myself coming back to the original Nintendo Gameboy (often referred to as the 'Dot Matrix Gameboy' or DMG) for several reasons:

  • The DMG board is really easy to work with; it is more spread out than boards in modern electronics, and even those with less-than-steady soldering hands can work on it.
  • The guts are well documented. The popularity of the DMG means that it has been turned inside out with very few mysteries remaining.
  • There are plenty of entry-level kits and mods that just about anyone can undertake.
  • The relatively low-cost of the DMG even today (one can typically be had for $30-$40) makes modding a fairly low-risk activity.

Of course, there's also my own sentimental reason: The DMG was my first portable game system. It went with me everywhere; from the living room couch, to long road trips, to the outdoors. The frustration of trying to get the contrast setting or lighting just right never outweighed the fun of Zelda and Pokémon on-the-go.

In the past, I've built simple backlit modded consoles for friends, but I've also been playing with some other common mods as well, including the "bivert" and crystal oscillator "clock-speed" mods. Both have limitations - the former doesn't include state-switching, and the latter only allows one or two single clock speeds to be utilized (unless you want to spend more money on hardware to replace the oscillator). Frustrated with these limitations, I've worked out some circuits to make each of these mods switchable. I then threw both in a single unit with an adjustable backlight, and called it a day (for now).

The results are satisfying:

A Side note: because I had my biversion "off" when I put my polarized film in, I forgot to rotate it for a proper bivert, so the "off" state is actually with the biversion on. Consequently, the screen contrast and sharpness will look even better when I get around to rotating the film.

A Side Side note: though you can't tell in the video (due to the frame-rate), the half-speed setting actually causes the screen to flicker (which is normal).

The switchable biversion

There's a lot of confusion around what constitutes a proper biversion (this video gets fairly pedantic about it, for those who are curious), but for the purposes of this mod, we're talking about the installation of a hex inverter chip along with a rotated polarized film (the first inverts the palette at a software level, the second inverts that inversion via the film). If you don't remove the backing on the DMG screen (typically done for backlighting), you can't do the second inversion (which makes a difference).

Most tutorials only cover a single-state configuration, but in reading the original (?) explanation for the mod, I noticed that the author had used a switch to toggle the biversion state without any kind of kit, which was totally rad and something I wanted for my Combo-mod Gameboy.

To start, I began with a chip install on my test unit:

DMG bivert mod photo 1
DMG bivert mod photo 2
DMG bivert mod photo 3
DMG bivert mod photo 4

I then installed a SPDT on/off switch on my circuit based off nitro2k01's photos and my understanding of these excellent biversion tutorials (which had clear instructions and great photos):

A quick test, aaand:

Success! My layout ended up being a bit different, but the results were just as effective:

DMG bivert switch mod photo 1
DMG bivert switch mod photo 2
DMG bivert switch mod photo 3

I recommend soldering the grounds to appropriate locations on the same board as the bivert chip, since crossing boards becomes a pain when re-assembling the DMG.

The 3-speed "clock speed" switch

I found out about the DMG "clock speed" mod fairly recently, and after seeing some examples online, decided I'd like to make my DMG with switchable speeds.

An important note about this mod: unlike the biversion switch, the clock "modes" cannot be changed on-the-fly with this configuration; the system must be powered down first. Not doing so will result in unceremonious power failure.

I started with this great overview of the mod, and simply updated the switch layout to accommodate 3 states instead of 2:

bivert switch diagram

Then, making use of a SPDT ON-OFF-ON rocker switch, some 2.097152 MHz (½x speed) and 8.388608 MHz (2x speed) crystal oscillators (you can get bags of these for a couple bucks on ebay), and a bit of solder, I had a working proof-of concept:

DMG oscillator clock speed switch photo 1
DMG oscillator clock speed switch photo 2
DMG oscillator clock speed switch photo 3

The results were very satisfying, but if I were to do a speed mod again, I'd definitely use a smaller switch, or even better, a Potentiometer-based speed mod (LTC1799 precision oscillator + Potentiometer to allow for on-the-fly adjustments along a range of speeds) instead.

Color-adjustable backlight

At this point, I had become quite familiar with the DMG backlighting process, but given my penchant for adding complexity where it isn't strictly necessary, I decided to do something a little extra special this time around. Kitsch-bent sells these RGB LED backlights ("RGBx3") capable of on-the-fly color adjustment with the right kit ("RGBva"), so I picked up a set to try.

The process is basically the same as any other backlight installation, though installing the RGBva adjustment controls required the extra steps of drilling (which I mostly got right) and mounting to the inside of the case.

By the way, THIS photo (taken from Kitsch-bent's site) shows the correct way to solder these (the pdf instructions were super ambiguous, and the photos were unclear).

Putting it all together

While all the mods at this point technically worked, I had neglected the thought experiment that is making it all fit inside the sealed DMG case. There was a fair amount of moving components around, hot gluing, and taping down wires. After trying a few different layouts, I was finally able to close the DMG without any undue stresses to the components inside.

DMG combo mod assembly photo 1
DMG combo mod assembly photo 2
DMG combo mod assembly photo 3

I put the bivert switch in the top right of the console, where it didn't quite sit flush with the case, and the clock speed switch on the bottom right side, which, given its size, made holding the DMG while playing a bit uncomfortable (given the large size of the switch). I've since acquired a smaller SPDT switch at the same size as the bivert switch. If I were to do this again, I'd probably look to place both switches next to each other somewhere near the top of the console.

DMG combo mod assembly photo 4
DMG combo mod assembly photo 5
DMG combo mod assembly photo 6
DMG combo mod assembly photo 7

One of the aims I had with these mods was to avoid some of the pricey kits that are out there that achieve the same or similar effects. That said, if you have the funds and want to build something really nice more easily, kits are a fine option.

Other Mods

This Combo-mod project certainly isn't representative of all the types of mods out there (one really popular mod I skipped was the "RCA Pro Sound" mod, which enables better and more ranged sound output options). The community is still quite active and always coming up with new ideas. There are now multiple online stores that offer glass screens, improved internal speakers, backlit buttons, and more.

There's a balance to be struck I think, however, between making your DMG fresh and useable, and replacing every component until there are barely any original parts. I'm much more reticent to backlight a Play-it-Loud edition DMG in good condition than a broken (but restorable) unit recovered from a Goodwill. When you get to the point where your hardware is more new/custom part than original, you might consider some of the Raspberry Pi-based RetroPi projects (like PiGRRL) as a different means to similar ends, but with even more features.