MOD: Mega Drive 2 PAL 60Hz color fix with a 2 pin crystal

I wanted to share this oscillator schematic for a colorfix to the MD2. Useful if you - like me use a pic (Link: Matt's code) to switch between 50/60Hz instead of a physical switch, and are unable to find 4 pin oscillators with the correct frequency.
Works great for me, let me know how/if it works for you.

You need to cut the trace before R61 to disable factory clock going into the videoencoder, and connect this circuit to R61. This forces the videoencoder to output PAL50/PAL60.
R61 is located in the top left corner of the MD2 motherboard.

Parts needed:
1x 1M resistor
1x 200R resistor
1x 30pF ceramic capacitor
1x 50pF variable capacitor
1x 4.433619Mhz 2 pin crystal
1x 74HC04 Hex inverter
Some wire

 

What about a fix for a switchless region console???

 

Pic with Matt's code = switchless


Here's a pic of my installation of above circuit.

 

This is the same as the circuit in use everywhere, but with a hex inverter to buffer the signal?

http://www.mmmonkey.co.uk/mega-drive-1-pal-60hz-colour-mod/

Or am I missing something?

 

As I understand it the hex inverter acts as a crystal driver which the MD2 videoencoder lacks. The MD1 encoder has a built in driver so it's easier to mod for PAL color.
I'm far from an expert on this so someone with more knowledge could perhaps explain better

What I do know is, it's near impossible to find a schematic that works for the MD2 (Except using a 4 pin oscillator). This one does.

 

Just BTW I found a seller on Aliexpress that has 4 pin oscs - here's a square version: http://www.aliexpress.com/item/10PC...-21-13-21-5-08mm-Square-active/949416078.html - they also have the rectangular version

I haven't received my order yet, but I don't anticipate any problems.

 

seems a cool mod.

 

I seem to remember correcting colour in the old days (for RF) with a crystal, transistor and I think there was a resistor and capacitor in there, too.

I'm not sure why you wouldn't just use RGB if you're in the UK, though. That's the best option all round. No mod needed and it's a better picture.

 

Sure, RGB is the best. But not everyone wants it or have RGB scart on their TV. Always good to have options

 

I've always used the 4-pin oscillators for my colour mods on MD1 and MD2 consoles, but always good to have an alternative!

 

CXA1645 and CXA2075 do not have Quartz Crystal oscillator driver. The circuit posted on mmonkey won't work with them. Also the crappy Samsung chip, but I don't think that one can do PAL video anyway lol.

 

I'm tired of attempts to correction Colour for MegaDrive 2 VA4, All attempts were used on the Internet and did not get a result i used oscillator's and crystals and everything did not get a Colour with switching from Pal50 to Pal60. After that I saw the chip SONY CAX1645M its same in the PSX 5502 so i moded MegaDrive 2 VA4 and used PIC 12C508/P with 2 pin Crystal it's work prefect

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Like I said the mod at mmmonkey is fail simply for not explaining it is ONLY FOR CXA1145.

 

I'm sorry for re-upping an old topic but did you program the PIC with a special code or just leave it as is? I suppose it will work as a Crystal driver but I don't understand how.

 

Hello

Has anyone managed to replicate this yet?

I am looking at 74HC04, I can see ping 1A, but not 1B?

Which pins exactly on this IC do we connect to?

 

Yo,

I made the mod on 2 Genesis 2, my board is kinda in work in progress.
So I made a board for the Genesis 2 which auto switch to PAL or NTSC Color Crystal subcarrier. It's an adaptation of a similar board I designed for the Genesis 1, but with automatic function (the other use a switch to allow forcing signals)
Here's the scematic:

Here's a exemple of a board. I'm not happy of the current design, but at least it corrects the flaws of my earlier prototype

- You need: Ground, +5v, Video signal (named as MB7), Original Crystal signal (named as MB6) , feed to the video chip (named as PIN6). I found a great place at R61 and removing it (my board includes the R61 as the 10k resistor)
- It analyses the signal incoming to pin 7 of the video chip (or from the JP3/4, it's the same signal), compare to another logic (Low or High) and a 74HC052 will "open" one or another circuit with the proper Crystal:

• if identical, uses original crystal signal
• if not, then if ground uses PAL
• if not, then uses NTSC

- Since the Genesis 2 doesn't have a Crystal Driver, and 2 pins Crystal are more easy to find than 4 pins (especially 4.43Mhz ones) I had to use a 74HC04 as a driver.
- It works fine with my switchless board, but since it's based on the NTSC/PAL logic on pin 7 it could easily fit with your switch mod.
Tested with two Genesis 2 VA1.8, one with a Fujitsu MB3514 and the other with a Samsung KA2195D. I've order two Sony CXA1145m to have a decent output and made some Svideo mode .
Here's some pics of the installation:


Note that it works perfectly with the KA2195D, but the MB3514 doesn't like "on-the-fly" change, but works fine on cool boot.

 

Wow, that mod looks awesome!

Good work!

I am doing just a normal toggle switch 60 Hz mod on my PAL console.

Next is to build a color fix circuit, for which I have just ordered components off eBay.

I will be using the schematic provided in the first post, hopefully it works?

I see you have two such circuits in your mod, so they definitely work?

Thanks

 

Yes it will works.
My mod is like the scematic in the first post, but twice (one for Pal, the other for NTSC) and an autoselection between them.

 

So have you got it to work with the other encoders? Is that schematic the final build of it?

 

I've quickly tried by swapping both of the Samsung and the Fujitsu by a Sony CXA1145M (for Svideo Mod). I had video issue due to the differences of resistor/capactiors around the video encoder, but it works.

The only one left to confirm is the Sony CXA1645.

I was busy with work and a lot of Snes repros, but I'll eventually made a post on Sega16 and here to share my work.