I've modded a lot in the past and mistakes are rare, it is still satisfying when it works the first time. My first ever hardware mod was to overclock an old Macintosh (25MHz to 40MHz bump) and I've done a number of AV mod on older consoles. Also did some controllers hack such as Atari 5200 paddle for a few 5200 games like Breakout, and adapter that lets me use PCE controllers on my TG-16 console. (reverse exists officially when NEC mad adapter to use TG-16 controller on then-new Turbo Duo). Lastly I converted a few NES carts to EPROM for playing rare games and for Earthbound. I figure by now I did over 100 mods
To date I've had only 3 failed mods. One of my Atari 5200 never had color on AV mod even though it still worked fine with RF, and the wiring was correct so I never finished it. Could have been a bad transistor or resistor?
I tried to mod a NES to have both NES and Famicom connector. It smoked on the first power on test, I guess I missed a short somewhere. This mod was before there were cheap NES/Famicom clones on eBay and I never tried this again since then, too much work with 132 wires to check and solder in.
The third failed mod was to convert Intellivision to use standard EPROM for playing burned games. Intellivision has really weird address system and can't be used with EPROM directly like most other cart based game systems. I never got it to work so I think I had bad data from schematic on prototype Intellivision cart which had EPROM.
If anyone know of a good schematic of Intellivision EPROM cart, I'd like one as I wanted to build one into console with EPROM sockets instead of regular cart connector.
Anyway I spent over an hour doing switch mod on my TG-16, most of them double checking the wiring to make sure I didn't cross it or short it. it worked the first time i tried =)
I went with the 8PDT switch version because it's less wiring, less soldering, and the IC switch method has too many tiny SMD contacts to solder with a $10 radio shack soldering iron. Beside TG-16 has lots of empty space inside, I put the switch behind the cart connector and the button is visible around the side.
Next: S-Video mod. Later: built in memory save function.
The memory save function (present in CD base or Turbo Booster PLUS) would be useful for future portable TG-16 mod (though I'd probably use a Coregrafx due to smaller board size) so I don't need to lug around the bulky devices. However there seems to be no schematic of the memory save system anywhere, so I'm taking my Turbo Booster Plus to reverse engineer it. I'll post the reverse engineering attempt in this thread:
http://www.pcenginefx.com/forums/index.php?topic=12653.0