After some fiddling around I managed to modify my trusty old nomad to output a true PAL 50hz signal so that I can play my Australian and European games on it. This was done by firstly changing the pins on the CXA1645P/M so that it outputted PAL colour this was done by changing pin 7 and pin 18. Pin 7 needing to be lifted and earthed while pin 18 is lifted and connected to ground through a 16k resistor.
This will Set the CXA1645P/M to PAL mode however there is a catch, the colour subcarrier frequency is still NTSC and as such the image you get will be black and white. To solve this I removed the NTSC frequency crystal oscillator from the lcd driver circuit and replaced it with a PAL 4.4336mhz subcarrier crystal.
I then tapped from the crystal occilator output and ran it into the lifted pin 6 on the CXA1645P/M.
The Nomad will now have a perfect PAL 50 output with colour, this is essential for me as my whole collection is PAL. Obviously I changed the region and frequency jumpers to suit my collection which is predominately Australian. If you’re not sure how to change the region jumpers there are countless really good tutorials out there.
Why did you lift pin 6 and connected externally the clock when the old oscillator was aleardy connected to pin 6?
It was being driven by the GPU oscillator which was still running at the NTSC subcarrier rate, I simply soldered my new PAL colour subcarrier crystal in place of the now redundant LCD driver crystal (only to save space and wiring) and ran a wire straight to the lifted pin 6. unfortunately the video chip requires the 4.4336mhz subcarrier input when running in PAL output and I couldn’t for the life of me find a source anywhere on the board.
I might answer my own question – because clock on pin 6 is not coming from the 2 pin crystal, but from a divider from the master clock (4pin) ??