PAL Megadrive I or II complete NTSC conversion question!

[John_Smith]

Hi there all! I'm in Australia and although we traditionally use the PAL standard here, we unfortunately don't have the nice compensation that is SCART RGB clarity (like the UK and Europe!) to make up for the reduced game speed and sqashed picture size. So it's basically a Composite and S-Video solution all the way and what I want to know is how to completely convert a PAL megadrive I or II over to NTSC in not only the 50 to 60Hz factor, which I have under control already, but to get the video encoder chip to display the damn picture in colour at 60Hz instead of going all greyscale on me!!! Any help would be great guys

 

[moonwhistle]

Sounds like your TV isn't 60 hz compatible.

I thought the 50 / 60 HZ swtich was the equivalent of PAL / NTSC. The language switch is merely another region lockout, it makes no difference to the vast majority of games once they're loaded.

 

[Dreamcazman]

I had the same problem. I tried the 60Hz conversion a long while ago and while it did run in 60Hz, the picture was B&W. I have a NTSC compatible TV as at the time I also used it to play my US Dreamcast on.

I never bothered trying to fix it as I don't use my MD much anymore.

 

[sQuareh4t3r]

I could be incredibly wrong (and I probably am), but to truly convert it over into 60Hz wouldn't you have to replace the PAL video crystal with an NTSC video crystal? I remember reading something about that before in regards to converting a PAL Neo into an NTSC console. Run some searches about NTSC conversion/PAL conversion in this forum and see what you come up with. Hope this helps.

 

[John_Smith]

Sounds like your TV isn't 60 hz compatible.

I thought the 50 / 60 HZ swtich was the equivalent of PAL / NTSC. The language switch is merely another region lockout, it makes no difference to the vast majority of games once they're loaded.

Hrmm....doesn't seem to be much of an issue these days, most of my consoles are US and JPN imports and all play fine and in colour on my TV's though it would make complete sense other wise. In regards to the suggestion on the swapping over of the video signal Crystal/Oscillator, that makes complete sense, but there appears to only be one present on the PCB and its like 53.whatever MHz, I figured it was more likely for the horizontal refresh rate than the PAL vs NTSC frequency. I also played with the video encoder chip's NTSC/PAL selector pin and pulled it high for NTSC rather than low for PAL and still no go!! Surely its possible to completely convert it to NTSC, ARGH!!!

 

[Phix]

Hmmm

I know you are going to be using s video / composite but what are you using to display it now ... ?

 

[John_Smith]

I know you are going to be using s video / composite but what are you using to display it now ... ?

Currently I'm using either S-Video or Composite as I've added external ports for these in addition to switches for language and 50/60Hz. I've tapped the signals direct from the video encoder chip (its a megadrive II and the chip seems to be based on the sony CXA1645M chip, though I think its a Fujitsu part). Both video standards work beautifully when in 50Hz mode by the way, oh and I've added an RGB port so I can use it on my arcade CRT, which displays in colour in either 50 or 60 Hz as (I guess ) the PAL vs NTSC thing has no baring on this direct signal. Not much good if I want to take it to a friends place n the like though......doh!

 

[sQuareh4t3r]

Dude, if you really want an NTSC Genesis that badly, why not just buy one? Hell, I can go get one and get it sent over to you for $30~$35 shipped. That would probably be a lot less time-consuming and tedious than trying to convert a PAL unit. Let me know.

 

[MKL]

The 1st version Megadrive has the same video encoder as the Neo Geo, namely a Sony CXA1145, so it should be very easy to convert it from PAL to NTSC by replacing the crystal and connecting pin 7 to +5v instead of ground. If you have a MD with a CXA1645 it can be different but still possible. Can you take a hi-res close-up of the encoder and surrounding components?

 

[John_Smith]

Dude, if you really want an NTSC Genesis that badly, why not just buy one? Hell, I can go get one and get it sent over to you for $30~$35 shipped. That would probably be a lot less time-consuming and tedious than trying to convert a PAL unit. Let me know.

Hehe yeah well ya never know I might just take ya up on that offer at some point, though for the moment (call me crazy), I'm enjoying the challenge.

MKL, I'll get right on the photo bit for ya so you can see what I've got to work with.

Cheers for the help guys!!

 

[John_Smith]

The 1st version Megadrive has the same video encoder as the Neo Geo, namely a Sony CXA1145, so it should be very easy to convert it from PAL to NTSC by replacing the crystal and connecting pin 7 to +5v instead of ground. If you have a MD with a CXA1645 it can be different but still possible. Can you take a hi-res close-up of the encoder and surrounding components?

MKL heres some pics of the overall PCB, a close up of the encoder chip and the only oscillator/crystal I can see on the board, rated at 53.2034MHz. The fujitsu MB3514 encoder chip seems to be based on the CXA1145 rather than the later 1645 to correct my earlier belief. It lacks a the Y trap and has no in built Chroma Bandpass Filter or Luma Delay line. It also has the audio in and ouput pins like the CXA1145.

Heres a URL to the data sheet -
http://www.fulcrum.ru/Read/CDROMs/FUJITSU/1999.December/data/eds/e428020.pdf

What ya think????

 

[Dean]

MKL heres some pics of the overall PCB, a close up of the encoder chip and the only oscillator/crystal I can see on the board, rated at 53.2034MHz. The fujitsu MB3514 encoder chip seems to be based on the CXA1145 rather than the later 1645 to correct my earlier belief. It lacks a the Y trap and has no in built Chroma Bandpass Filter or Luma Delay line. It also has the audio in and ouput pins like the CXA1145.
What ya think????

The MB3514 is exactly pin compatible with the CXA1145. You can use the "Neo Geo S-Video" mod to get the best picture with that chip.

I think you're also confused as no video encoder has audio in and out.

As far as swapping the crystal, I'm not 100% sure it's necessary, is it? When I install a 50/60 switch on a Genesis, the screen rolls and is B&W when switched to 50 on my 60 Hz TV. I believe the correct frequency is obtained from a higher frequency crystal by a conversion on the board. NTSC circuits like the CXA1145 take either 3.57845 Hz for NTSC or 4.4 something for PAL. You can see the oscillator on board is 53 and something. So I'm not entirely sure you need to replace the crystal.

 

[Devilman78]

The MB3514 is exactly pin compatible with the CXA1145. You can use the "Neo Geo S-Video" mod to get the best picture with that chip.

I think you're also confused as no video encoder has audio in and out.

As far as swapping the crystal, I'm not 100% sure it's necessary, is it? When I install a 50/60 switch on a Genesis, the screen rolls and is B&W when switched to 50 on my 60 Hz TV. I believe the correct frequency is obtained from a higher frequency crystal by a conversion on the board. NTSC circuits like the CXA1145 take either 3.57845 Hz for NTSC or 4.4 something for PAL. You can see the oscillator on board is 53 and something. So I'm not entirely sure you need to replace the crystal.

Actually the CXA1145 does have audio in/out. It's on the datasheet.

 

[MKL]

53MHz is the main clock, not related to the video encoder, so replacing that is out of question. You could follow the trace that goes to pin 6 (crystal in) of the encoder and see where it goes.

 

[Superfamifreak]

If you want to use composite on an MD1 you can easily hardwire it onto the mother board. To do this, turn the board over and look at the AV port. It should look something like:

And it doesn't take a genius to work out where the audio lead is wired on.

If you want stereo sound, just hook it up to your TV/Stereo through the headphone socket.