I can do a few different mods here. The easy: LED single color any where on the console, or a color changing LED, like this one.
$5 for single color LED.
$7 for color changing LED.
Or I can have the TG16 logo light up!
$25 for LED lit logo.
In order to play Japanese games you have to have a converter, sometimes you can find them on ebay, but not cheap.
OR, you can have the converter built in and switch between US and JP with the slide of a small switch!
In the picture below it's the switch in the 3-4 channel select hole!
Composite Video + Stereo:
The TG16 already has composite video and stereo outs, but you have to find one of the attachments to have the jacks: TurboBooster, TurboBoosterPlus, or a CD dock station. All of which are rare and expensive. If you just want composite and stereo RCA jacks put on the back of your TG16 I can install them cheap.
I also do a TRRS (headphone) jack style AV mod much like I do on the NES-101, see the pic above, the trrs jack has replaced the RF output rca jack!
Youtube Video of the region and AV mods:
TurboGrafx 16 TG-16 - LED lit logo - region mod - AV mod - How to's
If your system won't power on and you're sure the a/c adapter is good then the internal fuse could be blown, easy fix.
Since the TG16 is an RGB capable console, a component output mod is on my list of mods to try.