Modding Megadrive to 60Hz + NTSC colour

t0nito

Hi guys, I'm new to this forum, and as a first post, I'd like to contribute by showing you how I've done this mod.

This mod not only allows you to switch regions AND 50Hz/60Hz with only one switch, it will allow you to choose between PAL colour or true NTSC colour compatible with any capture card, multisystem, or even American TVs.

So here goes:

First I've done the 1 switch region mod following this tutorial:
http://mdpal60.net/wiki/megadrive/regionmod/start

Now here's what I've done differently for the other tutorials.
Every single one tells you to bridge pin 1 to pin 7 on the CXA1645 video encoder chip to force to PAL mode and add a 4.43Mhz crystal to make it a PAL 60 signal.

But since I have 3 NTSC compatible TVs and I wanted the console to output proper NTSC instead, I installed a 3.579 MHz crystal to the Mega Drive to allow NTSC colour on 60Hz mode.

I used a SPDT (single pole double throw) switch to choose from the original signal (Mega Drive's own 4.43 PAL and the added 3.58 MHz crystal.

Unlike the other mods you DO NOT BRIDGE PIN 7 TO GROUND on the encoder chip, we wan't it to be able to switch between PAL and NTSC when selecting 50 or 60 Hz.

The result is true PAL on 50Hz and true NTSC on 60Hz also the switch allows me to disable the crystal when using RGB to avoid interference.

Here's the schematic:



I wanted to add the switches in a nice and discrete place, so here how I did it:



And here is the result:

I really liked doing this mod, and if you wan't to do it on your console I hope you enjoy it too.

t0nito

"The result is true PAL on 50Hz and true NTSC on 60Hz also the switch allows me to disable the crystal when using RGB to avoid interference."

I have to make a little correction. I wrote this because every tutorial I read or seen on youtube say that the PAL crystal they add for PAL 60 causes interference when using the RGB cable.

I also seen pictures with those dreaded jailbars when using RGB on unmodded systems.

Well, today I received my RGB cable and I was pleasantly surprised, not only my NTSC crystal doesn't cause interference it eliminates the jailbars completely!!!

Unfortunately I don't have any capture card that supports RGB but I took photos of my LCD TV, with DNR turned off and sharpness high for the jailbars to stand out for comparison.

RGB 50Hz original PAL setting:



Ugly jailbars really noticeable.

RGB 50Hz NTSC crystal:



Faint pattern still noticeable especially on the darker shades of green.

RGB 60Hz original setting:



RGB 60Hz NTSC crystal:



Completely noise free crystal clear image!

Pretty cool huh?

Myrddin

Good job