The old lightning tube on an Atari Lynx is pretty terrible. Replacing it with a back-light is cost-effective and increases the screen visibility. This is fairly simple to do, but does require some soldering.
If you want to increase battery life, you'll probably also need to remove the coil, etc (not covered here). And you'll likely also need to replace the capacitors (also not covered here).
I got the LED light from handheldlegend.com if anyone's interested.
Step 1: Remove Battery Cover
Remove Battery Cover
Step 2: Remove 4 Screws From Back
Remove 4 Screws from Back
Step 3: Remove Hand Pads
Remove Pads on back of Lynx II to expose screw holes.
Step 4: Open Up Unit.
Open up unit (careful not to unplug ribbon cables) and remove internal battery case.
Step 5: Remove Back Plastic Cover.
Remove back plastic cover and prop up board to work on front of unit.
Step 6: Find Positive 5v Solder Point
You'll find the 5v solder point here, toward the top of the board on the back. You'll need to fold back copper sheathing to expose the board.
Step 7: Remove Screws From Light-Tube Assembly
Back on the front of the case, remove the four screws around the light-tube casing.
Step 8: Remove Center Screw From Screen Assembly.
Remove center screw from screen assembly.
Step 9: Test LED Unit
This would be a good time to test the LED unit. I soldered the positive to the 100 ohm resistor and touched the two wires to ground/solder-point while the unit was powered on.
Step 10: Disassemble Light-tube Casing.
The assembly is held together by twisted metal tabs. Reverse these to pull apart and try not to damage these, as they can help in reassembling. I had to cut one (used hot-glue to put the case back together later on).
Step 11: Pull Apart the Lighting Assembly.
Pull apart the lighting assembly.
Step 12: Remove Light-tube Assembly Side-boards.
On the tube-assembly, cut the wires and remove the two side boards. We need to keep the plastic mirror on the back so don't damage it.
Step 13: Cut Light-tube Wires.
Also cut the wires going to the tube.
Step 14: Remove Light-tube From Assembly.
Carefully remove the tube and you should have only the plastic mirror left.
Step 15: Examine LED Back-Light Vs Diffuser
The light diffuser (piece of white plastic) needs to be replaced with the LED backlight. They're almost the same size fortunately.
Step 16: Fit LED Back-light to Assembly Back.
In my case, I needed to remove these little plastic tabs to be able to slide on the LED back-light.
Step 17: Glue LED Back-light to Assembly Mirror.
Use glue to hold the back-light in place. Remember that the diffused, rough side goes forward (it may be covered by a plastic film - which must be removed).
Step 18: Put Together Display Assembly.
Reassemble everything. Use an air can to remove dust between the glass and the back-light. I also had to glue on the front padding.
Step 19: Clean Dust/oil From Screen.
Now clean the front of the class and make sure there's no dust particles (like between the glass and back-light).
Step 20: Add Middle Screw to Assembly.
Now replace the middle screw holding the frame to the assembly. (Notice I used hot glue to hold together the tab I had to cut. I quickly cooled the glue with the air canister upside down for this.)
Step 21: Screw Assembly Back to Front.
Now put the assembly back down on the case front. and add screws to hold assembly in place.
Step 22: Attach Ground Wire to Speaker Ground.
Connect the back-light ground wire to the speaker ground (this is common ground so it's fine).
Step 23: Add 100 Ohm Resistor to 5v Solder Point.
Now cut and solder the 100 ohm resistor to the 5v ground solder point shown here.
Step 24: Use Tape or Heat Shrink to Shield Positive From Ground.
Find something to shield the positive wire from the board and from the shielding (both of which are grounded). I chose shrink tubing - which I added to the positive wire before soldering to the resistor.
Step 25: Solder Positive to Resistor End.
Now solder the positive wire to the resistor.
Step 26: Apply Shielding Material for Positive Wire.
Apply electrical tape (or a lighter to the shrink tube) to shield the positive wire to prevent a short.
Step 27: Add Internal Battery Case Back.
Now start reassembly. Put back in the internal battery case
Step 28: Finish Back Assembly.
Add the four outer case screws and reattach the rubber hand pads.
Step 29: Add Battery Cover.
Reattach the battery cover.
Step 30: Enjoy Your Lynx.
Enjoy the modded Lynx. Games are still somewhat faded (even with replaced capacitors). But it's a lot better than the tube lighting. The light is constant but the contrast can fade in and out the LCD graphics.