Thought I would put this up as I haven't seen it around (doesn't mean it isn't I suppose lol).
Start of story-
For my birthday, wife asks what I want. Answer I would like a Nomad! (for modding of course). They are expensive in Australia, so I sourced one from America.
I also want it fitted with a LCD screen and region switch.
I planned (and I do expect to be criticized) from the start to have my region switch as a manual region switch (AU, JPN, USA), rather than pressing mode etc as some PAL games aren't keen on that sort of thing (screen scroll/flash etc)
Anyway I got the Nomad and LCD and I knew if I did the mod I would be visited by the black/white screen fairy. Had a few chats with TmEE about it and gave me the general idea.
I installed the LCD screen and initially I locked the video encoder with a 4.43(blah blah)Mhz 4 pin oscillator. The screen I got worked, buuuutttt I wasn't keen on the look of PAL60 (US and JPN region), the images seemed to have a "ghost" image around them, making it looked slightly smudged. When the switch was set to AU (PAL) the image was fine. Perhaps the LCD monitor, whilst being ok with NTSC and PAL(50) wasn't 100% happy about doing PAL60.
Anyway I got to work about re-wiring it all up so that the standard clock would do it's thing while the added oscillator would do the other thing.
First pic is where you can disable pin 6 to the CXA1645 video encoder, you could lift the leg if you want to but this is MUCH easier and safer. Also shown is where you can grab GND and +5V for the oscillator
NTSC clock and power points.JPG
Oscillator as shown, grab the datasheet for what you need.
As above but wired up and partially insulated. I put this in the front half of the case under the A,B,C,X,Y, Z buttons, really no other place to put it. (I also wrapped it in electrical tape for insulation)
oscillator wired up.JPG
CXA1645 video encoder, disable pin 7 up the line as shown. +5v selects NTSC mode, GND gives you PAL mode. Jolly interesting to note that it pulls itself high (+5V) when not grounded, so you only need to switch in GND! Pin 6 is for clock signal.
Switch schematic, quick ACAD drawup of the switch I used which is a 3 position 4 pole switch (slide)