Monday, May 11, 2009

Game Gear LED Backlight Mod

The following is a guide to a recently completed LED backlight mod I made on my blue Game Gear. Why do this? The standard Game Gear gets only 2-3 hours of battery life on 6 AAs. This is not good, and is largely due to the flourescent tube which illuminates the screen. With the LEDs you can get around 8 hours of battery life! Be aware of two things: the LEDs are a focal light source, and therefore will most likely have slight hot-spots nearest to the bulbs (see image). Secondly, I have found the screen is generally dimmer with two bulbs. The bulbs themselves are plenty bright and capable of washing the screen out if you turn the brightness up, but because the light is not completely uniform the screen is dimmer farther from the bulbs. Feel free to play around with more bulbs or different configurations - just adjust the resistor you use accordingly.

Please note that the mainboard depicted is not the original in the system - I replaced it with one from one of the Majesco re-releases of the Game Gear (better screen and audio). The Majesco boards have one primary ASIC controller chips, as opposed to the two on the original systems. If you have one of the original Game Gears, don't sweat it. This mod applies to either model.

I would also like to note that I did not develop this mod myself. A poster with the username of Tibia at the Benheck Forum was the brains behind this. She has also posted a guide, with much crisper images and her own instructions. The resistor I used in my mod is more conservative to ensure the LEDs don't burn out. The LEDs I used are also larger. Check her work out as well, and between the the two guides you should have more than enough info.

As Tibia also notes, you could potentially damage your Game Gear doing this. If you do it right, you shouldn't, but do this at your own risk!

You will need the following supplies for this modification (I've posted links to buy the less common parts):
  1. Soldering Iron
  2. Solder
  3. Screw drivers (philips, game bit)
  4. Pliers
  5. Hot Glue Gun or Epoxy
  6. Electrical Tape
  7. Wire cutters
  8. Wire
  9. Two 3.3V 5mm white LEDs

  10. 39 ohm 1/4 watt resistor
  11. Smaller sized heat-shrink
Step 1) Open up your Game Gear. This is mostly straightforward except for the security screw at the top center. You need a gamebit driver to remove this screw, or you can try to make your own tool for it ( Don't try to simply snap it, you can crack your screen that way. I've done it.

Here's the inside of the famous Game Gear. See those blurry red Xs? Those are the areas of interest. There are 10. The 4 components in the top left are dedicated to powering the CFL tube which currently lights the system. We will be removing them. We will also be removing the tube (obviously) and its resistors, marked by the 6 Xs around the reflector in the center of the system. Closeups are below.

Step 2) Remove all the screws mounting the mainboard to the case. The small screws passing through the white plastic right around the screen also hold the LCD to the mainboard. You should remove them to get the screen out of the way, but be careful when you do so it doesn't flop away and hit something or pull on the ribbon cable too hard.

When the screen is removed as far from the blast zone as the ribbon cable will allow, remove the reflector plate from the around the CFL tube. Now you can have some fun!

Step 3) Begin to desolder all the components marked above with the red Xs. Use the pliers to gently pull on the component while you melt the solder with the iron from the other side of the board. Some components will come off easily, like the CFL tube and the resistors. The large square transformer, however, might be difficult. Try to get the contacts on one side loose then work on the other. Do not throw out the rubber CFL tube endcaps. You will be mounting your LEDs in them.

Here's a shot of the side where all those components used to be. The Xs denote these locations. Take note of the light green circles I marked on the board.
  • The two green marks within the white circle need to be connected to each other. Solder a bit of wire between the two contacts to resolve this.
  • The green mark by itself on the left of the white square on which the transformer sat is a ground point. This is where your LEDs will be grounded.
  • The green mark in the center of the five contacts at the bottom of the white square is the current source. It is 5 Volts, for those interested. The 39 ohm resistor will be connected to this point.

Here's a shot of the other side of the board. Not much needed to happen here, just the removal of the CFL tube and its resistor. Those spots are again marked with the Xs.

Step 4) We now need to prepare the LEDs. I think it helps to sand the LEDs so that they have a milky-white appearance. This might help diffuse the light from the bulbs so they have less of a brightspot. Compare the one on the left to the sanded one on the right:

Now clip the wires of the LEDs relatively short, and solder your wires to them. Make sure the wires have about 5" length to them to allow for mistakes. Take note of which wire is attached to the positive and negative sides of each LED to avoid mistakes later. Use heatshrink to insulate the bare wire and solder. Like so:

Now feed the wires through the rubber CFL end-caps. Situate the LEDs so that the bulbs are submerged into the rubber caps (sinking them so the tip is flush with the opening of the end-cap has a better effect than the half-way position I've depicted here). Get them as nice and centered as you can, and fix them in place with epoxy to ensure your backlighting doesn't change with the movement of the car. It should look something like this:

Once the LEDs are fixed firmly in place, glue the rubber caps to the sides of the reflector plate. They won't stay in place otherwise. It should look like this:

Finally, connect the LEDs to each other in parallel. This means the positive wires from both LEDs are soldered together, and the negative wires from both LEDs are soldered together. From the unions of the positive and negative wires run a single wire to connect to the ground and power source on the board. The voltage source is 5v; there are numerous resistor calculators online for you to consider when trying to pair the LEDs you bought with appropriate resistance (in my case 25mah 3.3v wired in parallel: Try this calculator). I recommend trimming the LED wires on the side near the ground and power short to avoid excess cable in the case. Insulate the junctions where the positives merge into one and the negatives merge into one using heat-shrink so it looks like so:

Step 5) Now it is time to finish the job. Solder the resistor to the center of the row of five contacts identified above. Clip its ends short to keep a low profile on the circuit board. Position the reflector with its LEDs back to the mainboard, reposition the LCD screen, and use the screws to fix the two together on the board again. Solder the LED negative to the other end of the resistor. Now your LEDs have power. Solder the positive LED wire to the ground point on the board. Now the circuit is complete. It should look like this (only less blurry), indicated by the green lines:

Finally, we need to make sure the wires don't get in the way of anything. Use electrical tape to affix them to the side of the reflector, like so:

Your mod is complete. Put the Game Gear back together, pop in some batteries and enjoy the improved energy efficiency!

**EDIT** I have since pursued modifications to improve the dispersion of the backlighting (reduce the hot-spots and allow for brightness to be raised without washing the image out as much). So far, I've had LITTLE SUCCESS.
But stay tuned, or offer up any suggestions! Also, if anyone has images of an improvement on this approach, feel free to share and I'll put your work up. There seems to be a lot of interest in this modification.

**EDIT #2**
I have since tried an opaque white straw as a diffuser (POSTED HERE). But the results were unsatisfactory.