Region modded Megadrive black and white through RF AND Composite

[soop]

According to what I've read, the composite takes its sync from the chip (can't remember which one) rather than the 50/60hz timer, and that's what makes it black and white. But I've read that RF should actually be displaying in colour at 60hz, and that's black and white too.

What's the simplest way to mod the video sync to match with 60mhz mode? If it's a permanent change, that's fine, I intend to stick with 60Hz.

[playgen]

Use an RGB scart cable and you will get a colour image in 60hz.

[soop]

Use an RGB scart cable and you will get a colour image in 60hz.

That's an option, but I've really been enjoying tinkering, so if there's a mod which isn't over-complex and doesn't cost more than about £8 (the cost of a scart cable) I'd like to give that a go.

[Ace]

You would need to build a small circuit using a 2-pin crystal. a 15Kohm resistor and 2 ceramic capacitors, one of 30pF, the other of 50pF. I assume you've region-modded a European MegaDrive if the video is in black and white when outputting NTSC video? In that case, you'd need a 3.579545MHz crystal.

What you have to do is desolder pin 6 of the video encoder off of the motherboard. You have to solder one end of the crystal to pin 5 of the encoder, then solder the other end to a switch. Here's the datasheet for the Sony CXA1145: http://www.alldatasheet.com/datashee.../CXA1145M.html

Page 11 shows you how the CXA1145 should be hooked up in both a PAL and NTSC system(you'd need to look at NTSC in your case). But instead of hooking up one end of the crystal to pin 6, hook it up to an SPDT switch so you can switch back and forth between the PAL and NTSC color subcarrier frequencies.

You can't use this method on a Fujitsu MB3514, however, as it only has an input for a crystal. The CXA1145 has both an input and an output, so this circuit will work.

[ooXxXoo]

Also, you can have both 50 & 60Hz in color (with a compatible tv) with a proper switch ....

[soop]

Thanks - you're referring to this, right? http://zipplet.co.uk/index.php/conte...ronics_mdpal60 I think that might be biting off more than I can chew...

[Ace]

That's exactly what I'm referring to, but replace the 4.433619MHz crystal with a 3.579545MHz crystal. Since 60Hz is NTSC video, the proper NTSC color subcarrier frequency should be supplied to the video encoder. You might be able to get away with a PAL color subcarrier frequency and an NTSC video signal, but I doubt it.

[Jorge Nuno]

I did a mod similar to this to Oerg, however I used a divide-by-12 circuit to divide the master clock for PAL, irrelevant of whatever region the MD is set to. PAL / "NTSC 4.43MHz"

This is actually what the 32x does when it's region modded, because the crystal is fixed. And yep I get color, but some TVs could reject it, I don't know...

[Mamejay]

http://www.retro-otaku.com/2010/07/p...e-and-s-video/
Easy done just using a crystal oscillator. Just need to cut a track to and feed in the new signal. All screen will be displayed in colour.

[soop]

http://www.retro-otaku.com/2010/07/p...e-and-s-video/
Easy done just using a crystal oscillator. Just need to cut a track to and feed in the new signal. All screen will be displayed in colour.

Perfect! Cheers

[Jorge Nuno]

That oscillator may be hard to find..

[Mamejay]

I found one locally in my Melbourne, Australia. I am sure you can find them everywhere if you look.

[soop]

They are proving REALLY hard to find.

[fr@ser]

Couldn't you just use a pic16f630 and set it's internal osc ?

[Jorge Nuno]

The internal PIC oscillator is a low precision RC-type and runs at 4 or 8 MHz, IIRC depending on model, so its totally unsuitable for PAL/NTSC things...

However any PIC can be used to make a crystal oscillate. But you also need a programmer to burn the empty binary + configuration bits (where the oscillator configs are stored, among other things). This is totally unnecessary, its way easier/cheaper to use a 74HC04 inverter