McWill Game Gear "Full Mod"

Nearly every handheld console released between the original Game Boy and the DS has some kind of screen mod available to replace its original LCD technology with a "modern", backlit, high speed LCD. This is mostly because early LCD technology had a lot of shortcomings, from washed out colors, to slow, low contrast LCD cells, to complicated high-voltage fluorescent backlights that severely limited viewing angles. The oldest such modern screen for an old handheld I can recall is the "McWill" LCD mod for the Atari Lynx. 

The Lynx "McWill" mod was nigh legendary because it was such a perfect match. The new screen was bright, responsive, exactly (or nearly exactly) the same dimensions, and used perfect integer scaling. It took the Lynx from a blurry washed out screen to a sharp and crystal clear display. Of course the first thing many people wondered after seeing it, was what options might exist for other, more popular handhelds such as the Sega Game Gear.  After all the Lynx and the Game Gear screens operated on very similar principles.  It wasn't long before the creator of the McWill Lynx screen mod began offering a McWill GG screen mod, incorporating the same bright, responsive LCD as the Lynx mod.

Unfortunately the Game Gear screen geometry did not allow for an integer scale with the new screen.  What is integer scaling?  Put simply it is the process of multiplying pixels by whole numbers before displaying them on higher resolution screens. For example, if the screen output was 320 pixels wide and 240 pixels high, the first integer scale would be to multiply both axis by 2 for an image that was 640 pixels wide and 480 pixels high - each original pixel would now be represented by four pixels of the same color. 

The original McWill Game Gear LCD had uneven scaling which meant that some pixels would be multiplied by 4 (2x on both axis) and others would only be multiplied by 2 (2x on one axis, 1x on the other). In motion this caused shimmering and warping of the image. Some people aren't bothered by this, but it was so distracting that I really never used the Game Gear I installed it in.

Why aren't the screens the correct resolution to do a proper integer scale?  None of the screens used in these mod kits were actually designed for this purpose. Screens are expensive to design and manufacturing requires gigantic minimum order quantities. The retro modding community simply doesn't do enough volume to make it cost effective.

Over the years other mod makers and companies have sold their own version of a Game Gear replacement screen. Each time I would see a new one announced it got my hopes up that someone had finally found a source of screens that would allow integer scaling, and each time after digging a little it seemed that the new mod was using the same old screen with its uneven scaling and shimmer.  That is until this year.  I saw a post on X giving impressions of the "New" McWill mod with a 640x480 screen that offered integer scaling. (While my intention with this article was to note that this was the first 640x480 GG screen option I was personally aware of, I have been informed a couple of times since originally publishing this post that there were others that pre-dated McWill's.)

My immediate question was whether I could swap out the old McWill LCD screen for this one. Unfortunately documentation was (and still kind of is) in short supply, so without doing a detailed analysis of both install processes, I'm legitimately not sure if the new screen can be swapped in.

Because of the voltages and signals involved, the installation process for replacing just the screen screen involves removing numerous components from the original motherboard, and generally requires replacing all of the electrolytic capacitors.  It's not the most complex mod out there, but it requires a lot of time and patience to do correctly. 

The Full Mod

When I went to buy one of these new screens from Console5 I noticed that they were offered in a "Full Mod" version, that essentially skips most of the tedium of the installation by instead offering a new motherboard, power board and audio board.  Rather than install a new screen into an old motherboard, you install the old ASICs (Application Specific Integrated Circuits - the proprietary chips that only Sega made that you can't really buy in a store) and the old CPU onto a new motherboard with the new screen already installed.

Since I had a GG in my bone pile that had already been mostly stripped for parts, I already had what I needed on hand.

Ordering from Console5 is always a pleasure. The proprietor is one of the most helpful people you will ever meet in this hobby. The Console5 wiki has installation instructions provided by "McWill", though the instructions are somewhat incomplete.

Things the instructions don't tell you:

• The LiPo batteries (not provided) are not optional. The USB-C port is ONLY for charging, it will not power the Game Gear by itself.
• What batteries to buy
• How to install the clock crystal (on its side)
• The plug type needed for the batteries is JIS ZR series with 1.5mm pitch. 
• Only USB-A to USB-C connections will work for charging - USB-C to USB-C will not charge.
• When the system LED is Blue, the battery is charging. It automatically shuts off when charging is complete.
• The topmost screw post in the Game Gear case (the one visible above the cartridge slot) must be removed for the new screen and motherboard to fit properly.
• How to safely remove the cartridge slot from the original motherboard
• How to properly align the cartridge slot to the new motherboard

Most of these are explained simply by me mentioning them above - now you know the batteries are required (I imagine Console5's product page has been updated with this info by the time you read this), you know that you have to use USB-A to USB-C cables for charging, and that you have to remove the screw post.  That just leaves removing the cartridge slot.

To remove the cartridge slot safely, obviously you need to start by de-soldering the cartridge pins with the appropriate tools.  When it comes to removing the rivets holding the edges of the cart slot to the main PCB, there's no apparent way to do this without destroying the rivets.  On the back side of the cartridge slot, use flush cutters to pinch the rim of the rivets inward until the rivets can be pushed out the other side.

To re-attach the cartridge slot, the slot needs to be held in place before the pins are soldered. The solution I used was brass round-head paper fasteners. After placing the cartridge slot onto the new motherboard, BEFORE you solder in the pins, push two round-head fasteners through so that the "head" of the fastener is on the cartridge slot, and the "legs" of the fasteners come out on the side of the PCB with the screen. Then bend the legs flat, pulling outward to create tension and hold the cartridge slot in place. This will ensure that the cartridge slot is properly aligned when you solder the pins. When done, you can remove the fasteners and use the screws to fasten the cart slot to the case when you re-install the motherboard.

The secret to aligning the cart slot for installation.

Insert the fastener into this side of the cart slot mounting hole.

Then pull the legs apart to create tension. This will ensure the cart slot is aligned properly before you solder the pins.

The way this "mod" supports either 2-ASIC or 1-ASIC Game Gears is very elegant. A "daughter board" PCB is provided for both variations. You simply transfer the appropriate components to the appropriate daughter board and then plug it in to the main PCB.  Unfortunately it is necessary to modify the main PCB a little when using the 1-ASIC board.  Because this is called a "workaround" in the official instructions, it seems possible this is something that might be fixed in a future revision of this mod.

2-ASIC daughter board populated with transplanted ICs and clock crystal.

The backside of the 2-ASIC daughter board showing the Z80 CPU transplanted from the original GG motherboard.

The daughter board slots into the motherboard like a RAM chip.

An interesting possibility that this "daughterboard" design creates is modders selling pre-populated daughter boards to folks without the skills or equipment to swap out those chips, and, possibly, sending your board in to be checked for errors.  I have no doubt this design also aided greatly in compliance testing to make sure each "mod" was working before being sent to installers.

Which Batteries?

Finding batteries is a bit of a mixed bag.  Firstly, ANY 3.7v LiPo battery will theoretically work to power the Game Gear. The new power board has sockets for two batteries - these are wired in parallel. The real trick is finding something that already has the JIS ZR 1.5mm plug, AND will physically fit into the AA battery cavities on the back case, AND will have enough watt hours for decent play time.

As of the time I started writing this article, I didn't have "proper" batteries. While I waited for some to arrive I wired a 103450 size battery with 6.66 watt-hours directly into the power board (because I also didn't have any JIS 1.5mm plugs).  By the time you're reading this, Console5 should have plugs of the proper size available with the full mod kit so you can purchase cheap LiPo batteries from Amazon and just replace the leads. 

As far as physical dimensions, if you want a clean install, the batteries need to fit fully inside the space previously occupied by 3 AA batteries. There are many sizes that will work, but I wasn't really able to find a good list of them.  The size codes seem to have something to do with the physical dimensions - for example  the 103450 I started with was 10mm X 34mm X 50mm, but the 604050 definitely doesn't follow this pattern.  If you want to absolutely maximize the space, you'll want to go with the 604050 size.

 

The 604050 battery is a tight fit in the original compartment.

Removing the ribs from the underside of the battery doors can give the LiPo batteries a teensy bit more clearance.  For the best fit you would also need to remove the ribs from the bottom of the battery compartments as well.

There are some LiPo battery packs you can find specifically made for other GG battery mods. Based on their appearance it seems that someone did the work of figuring out which batteries fit, then wrapped them in their own logos to obscure the size codes and sold them for around a 300% markup.  

With a single 6.66 Watt-hour (1800mAh @ 3.7V) battery I get a little over an hour of play time at full brightness before the low battery warning starts flashing.  The batteries I've ordered are supposed to be 3000mAh @ 3.7V which should be around 11.1 Watt-hours each for a total of 22.2. Extrapolating from that I'm expecting about 4-6 hour battery life. 

Screen Fit

One thing to note is that the new screen is not the exact size of the original screen. It's 4mm wider and 2mm shorter which means that when you install into an unmodified Game Gear case, the right and left of the screen are obscured by the edges of the bezel, and there's a thin dark area at the top of the opening.  For some reason the new screen isn't actually centered in front of the opening. Although both sizes of the screen are obscured by the frame, more of the right side is covered than the left. This is mostly tolerable as-is, but there are several games that utilize the screen all the way to the edge and this becomes annoying there. For example, it's impossible to see your full score in Columns because it's printed all the way to the right edge of the image.

Notice half of the "M" in trademark is obscured behind the frame. 

Notice the blue frame is chopped off to the right. The screen is outputting the image, but the original opening isn't wide enough to see it.

What's unfortunate is that there isn't really a simple way to widen the screen opening accurately.  What I ended up doing was removing the lens from the front of the case, and with the screen installed, placed strips of tape along the left and right sides of the screen right up to the edge that was visible through the screen. Then I removed the case powered it on with a game like Columns and measured the distance between the edge of the tape and the edge of the screen image.  

Based on my measurements I needed to remove 1mm from the left edge, and 3mm from the right edge. Again, why this wasn't centered so it was 2mm from each edge makes no sense to me.

Ordinarily I would not do this with an OEM game gear case because I don't like irreversible mods, but this case was already cosmetically beat up and was never going to look good again.

A 3-D printed template that snaps in place and only exposes the parts of the edge that need to be filed down would have been great, but what I had to do was to use calipers to mark the width, and strips of brightly colored tape to mark where the edge needed to be, then carefully file down the sides of the opening until they met the edge of the tape. 

The uneven width of the bezel on each side is rather obvious, but you don't really notice it while you're playing.

This is what it looks like with the bezel widened.

The "TM" on the right can now be seen in full.

The menu box is no longer cropped off on the right side.

Features I Did Not Use

This "mod" is chock full of features, but there were several I didn't really find useful in their current state.

• The pre-installed analog joystick required additional case modification, and the joystick ring was transparent so it just didn't look very good, so I removed it and stuck with the original D-Pad.
• There are LED lights on the motherboard next to each of the buttons. As far as I can tell these are purely cosmetic, and only really make sense in the context of a transparent shell install.
• Usually I'm a fan of the scanlines look, but in this case the scanlines are applied at the scaled resolution, so they don't align with the original pixels and therefore don't mimic the look of the original screen at all. They really just dim the image.
• There are spots on the motherboard to install D-Sub 9 controller ports for a "Consolized" installation, but this requires additional case cutting which I was not interested in.
• The link port has been replaced with an HDMI video port, however the "Player 2" D-Sub 9 socket is attached to the necessary pins for reconstructing the link cable. (Apparently the EXT port on the original GG is really just a second controller port.).

HDMI Output

The jailbars in the HDMI output are pretty extreme. 

Even with darker colors, the jailbars are still extremely prominent in the HDMI output

The built-in HDMI output on this kit is what I would call passable. It outputs a 640x480 signal which should resolve to the correct aspect ratio on displays that support it. Unfortunately "VGA" is no longer a common input format and many modern TVs don't support it. 

I don't really have a scientific way of measuring input latency but none was noticeable during my testing. 

Unfortunately the output is filled with jailbars, and has V-sync issues leading to frequent screen tearing.

On the plus side, this definitely seems to be the mode the scanlines were meant to be used with because unlike when output to the built-in screen, the scanlines in the HDMI out, seem to align with the pixel boundaries and look much better. 

SMS Support

This mod worked perfectly with my Master Gear converter to play Master System games. The games appeared in the correct resolution - also without any scaling artifacts.

New Sound Board

While the new sound board provides strong and clear sound from the original GG speaker, it also emits a constant low level buzzing which is something I definitely did not expect from newly designed PCBs.

In case this was being caused by EMI noise from the original ASICs, I created a makeshift RF shield with copper foil tape all the way around the daughter board, but it didn't have any impact on the audio buzzing.  The audio buzzing is not present/obvious through the HDMI output so it's definitely happening in the analog output stage.

There is apparently a 2-speaker version of the sound board available from McWill, however as of this writing it was not available through Console5.

Conclusion

The 640x480 screen is, by far the best Game Gear replacement screen option available which still uses original Sega hardware (even if the only original hardware it uses are the ASICs, CPU and cartridge slot). The Full Mod also comes with a number of premium features for people who really want to go all the way and trick out their Game Gear with custom cases and internal LEDs. 

Unfortunately it's far from perfect. The requirement to use difficult-to-source batteries instead of just being able to power it off of a USB-C power supply is a major drawback in my book, as is the fact that there is no reliable method for correctly re-sizing the frame to fit the new screen width. The noisy audio and HDMI output were also disappointments considering this kit has all freshly engineered PCBs which I expected would have accounted for and eliminated these issues in the design. 

Finally, the kit is not cheap, clocking in at just under $200 US before tax and shipping. By the time you factor in the price of shipping, tax, batteries and a donor Game Gear you're in the neighborhood of $300 (USD) in materials alone. If you want to use a fresh case with new buttons and a glass lens, you're definitely over the $300 mark.  This means it might be more cost effective to just buy an Analogue Pocket and a Game Gear adapter.  But the real question is: is it worth it?  If running on original hardware and integer scaling are important to you, then it definitely is. 

Pros:

• Provided you have the tools and the skill to remove the ASICs without damaging them, it's very easy to install.
• The installation is universal - works for any version of GG
• No capacitor replacement, no cleaning old potentiometers
• Never worry about electrolytic capacitors again
• Fully functional brightness potentiometer
• Built in HDMI output
• Motherboard has built in sockets for installing a Genesis controller port and replacement link cable.
• Jacks and plugs are angled to match the contour of the case

Cons:

• High cost - if you install it yourself it's close to the price of an Analogue Pocket & Adapters. If you have someone else do the work for you, it's going to be considerably more.
• Can't be installed with simple soldering tools - you need an SMD rework tool like a hot air station.
• Requires case modification.
• HDMI output is noisy and has jailbars
• HDMI output is at "VGA" resolution which is not supported by many TVs
• Audio buzzing
• Cannot (easily) work without attached LiPo batteries.
• Screen is slightly oversized compared to original
• Pixel aspect ratio is incorrect to the image is very slightly stretched horizontally