Hope this is in the correct section, if not can someone move it please?
I modded my Launch day UK PAL SNES years ago for 50/60 Hz and also did the LOCKOUT mod.
For years I had a US HORI SGB (Super GAMEBBOY) Controller Pad, but could never get it to work on my PAL machine, then I saw this page:http://www.gamesx.com/misctech/eurosnescontrol.htm
I did the mod but found that the LINKS were hard to see in the photos, so I have made new images. Basically the LINKS short out four Diodes.
Region MODS have got a bit more complicated now a days! but why Nintendo Region LOCKED the PADS is anyones guess!
Best thing is I had taken the HORI pad to bits years before and tried hacking around swapping wires etc in the PORT Connector, so I got my SMARTJOY SNES - USB adaptor and used that to get the connector PINS back in the correct order and IT STILL WORKED!, I did it using the USB adaptor to avoid damaging the SNES. once it was working in the USB adaptor and all buttons were working correctly I fired it up in the SNES and BEHOLD a working SGB PAD on a PAL SNES.