It may be one of the oldest pages on GameSX.com, but it still works. The TurboGrafx / PC Engine import mod (http://www.gamesx.com/importmod/necjapmod.htm) is simple, though getting past the shielding on these portables is a little tricky. Of course with this mod you still need a Kisado or similar adaptor.
(http://gamesx.com/grafx/TE-repair3-1.jpg)
Simple: Connect pin 29 to GND.
Remember this only needs to be done for Japanese units where you want to play US/PAL games. Keep this in mind before you waste time opening and modding a US system like I just did. It won't hurt, but it makes you feel like an idiot. =(
oh I know the pain of modding for no reason. I've built many amps to boost the rgb signal of one system (about 6 in total) and wound up just using only one for the brightness wire of the s-video cord..