Please proceed with caution, I will not be responsible to any damages that this mod or fix will do to your expensive radio. Since I dont see any quick and cheap fix for dark LCD problems on xtl5000 and xtl2500 radios. I managed to find the location where to adjust the contrast of the display module. I attached a couple of pictures of the work I did. There are 2 ways to do this, add a 10K resistor and 180 ohm resistor, or add a fixed 2.2K resistor. Detailed picture are shown of the parts and points location. You can experiment with the values of the resistors to get the desired contrast. I personally tested this on my GRAY head XTL5000 and managed to lower the contrast at desirable level. Again like I said earlier, Im not responsible if this mod will damage your radio. If you find this useful let me know and if not send me a message.