Flexible Multisystem Megadrive opinion needed

[t0nito]

Hi, even though I have a RGB cable I do have atleast 2 TVs that will only do composite. But stil I'd like to do this for fun as well.

At the moment I have a modded 50/60 MHz Mega Drive with a second switch to choose between original clock (PAL when 50Hz) or the 3.58 oscillator when in 60Hz but this limits me to use NTSC.

My goal is to be able to choose (especially when in 60Hz mode) if I want NTSC 3.58 or PAL 60Hz 4.43MHz

I made a diagram here and I ask for your opinion if you think it will actually work, especially the part where the 2 crystal oscillators are combined on pin 5 of the encoder.

To explain the diagram I have 3 switches (in addition to the 50/60Hz which is not here represented), one switch is to select which oscilator I wan't (3.58 or 4.43) and the other is to choose the type of encoding I want (PAL or NTSC) by floating pin 7 and toggling between ground and a 5V source.

This way I could have 4 types of encoding whether in 50 or 60 Hz:

- PAL 4.43
- NTSC 3.58
- PAL 3.58
- NTSC 4.43

The other switch is simply a crystal/chroma killer for when using RGB (if needed).

Hope it's not to confusing:



What do you guys think, should it work?

[TmEE]

[Joe Redifer]

[t0nito]

Cool! Thanks it actually makes thing easier and I save a resistor and a capacitor instead of using 2 sets of each!

[t0nito]

What is this 4th leg on the switch for? Chroma killer?

[TmEE]

It is 3rd state of a slide-switch. So yes.

[evildragon]

I lol'ed, a lot. XD

[t0nito]

It is 3rd state of a slide-switch. So yes.

Thanks! I was thinking of simply cutting clock supply to the encoder, so pulling to ground is better?

[TmEE]

Floating input will pick up signal, so yes grounding it is the way to go.

[evildragon]

I know quite a bit about floating signals. Lol

[t0nito]

Just to confirm (and in case anyone else is interested for future reference) is this correct?

[t0nito]

I've finally done the mod and it works exactly like I wanted! Thank you!

[Helder]

Necro Bump.

Was this tested and made on a Model 1? Reason I ask is that the Model 2 doesn't have a way to drive the Crystals like the Model 1 and extra components are needed or use a can oscillator for each frequency.

[t0nito]

Tested and working on my Model1 VA6

[zyrobs]