Converting a PAL-I SMS 2 into a NTSC-SMS 2

**ooXxXoo** · 03-09-2009, 01:46 PM

Howdy fellows!

I got this PAL SMS2 from a friend of mine and have decided to switch it from PAL to NTSC....

This particular board has a 315-5237 Asic and a MB3514 Encoder that I've never seen before but most likely very common in other parts of the world....Nevertheless,Installed and replaced the native PAL 53.2034Mhz Master Clk Oscillator with a NTSC 53.7Mhz one, modded the VDP clk from 10.64Mhz to 10.7386Mhz and tried to switch the MB3514 encoder from low to high (PAL/NTSC)...But I'm not getting any good results, the encoder video signal acts as if it wants to switch from PAL to NTSC but it won't fully lock... Any help or suggestion will be much appreciated....Does any pin(s) in the 315-5237 have to be changed as well?...I noticed some of the pins are just grounded..

**TmEE** · 03-09-2009, 03:02 PM

If you changed the master clock, you should really need nothing else to be done besides putting VDP into 60Hz and making the encoder chip output NTSC instead of PAL... oh, and you will need to find a pin that controls color subcarrier output of VDP or supply your own subcarrier to the encoder... it looks like you have done everything needed ?

**ooXxXoo** · 03-09-2009, 03:12 PM

Uhmmm....I did lift pin 7 (PAL/NTSC mode) and connected to Vcc, according to the MB3514 datasheet this is NTSC mode, and added a 3.5795 hz xtal input as well....I'm really breaking my head on this one....

**TmEE** · 03-09-2009, 03:21 PM

you're still getting black and white image ?

**ooXxXoo** · 03-09-2009, 03:34 PM

yeah...Black & White, but the color slowly comes and goes at times, as if it wants to kick in... Are you aware of if any pins in the 315-5237 have to be disable/enable in order to work in NTSC mode?

**TmEE** · 03-09-2009, 03:43 PM

it kind of seems that the clock you use for the encoder is not accurate enough, does the coming and going is regular with same intervals ?

**ooXxXoo** · 03-09-2009, 04:25 PM

That's what I was thinking, so I'm ging to try a few different ones and report back later..

**ooXxXoo** · 03-09-2009, 05:30 PM

After trying a couple different crystals, nothing...This MB3514 still is booting in PAL with a NTSC twist...

TmEE, what sort of buffer will you recommend for the MB3514 PAL/NTSC switching mode?....

**TmEE** · 03-09-2009, 05:46 PM

What do you mean by buffer here ? Having the select pin in either GND or VCC is what is is needed, and since you're seeing colors in some point, it works (if the chip is in PAL, you'd not get any colors and possibly no meaningful pic as NTSC is much different from PAL). Only problem is the crystal... I guess you have nicely disconnected the existing color clock from the chip, so it does not get in the way...

**Ace** · 03-09-2009, 05:55 PM

Now, hold on just a second, doesn't the Master System change the color subcarrier when it's switched between PAL and NTSC mode? I don't know if it works the same way on a Master System II, but I switched my Master System I and it outputs full color video in both PAL and NTSC. I'd have to check that out on my NTSC Master System II.

**TmEE** · 03-09-2009, 06:10 PM

The VDP pin only changes refresh, color freq stays same.

**ooXxXoo** · 03-09-2009, 06:25 PM

Unfortunately, the SMS 1 and American SMS 2 that I've seen for that matter, have a different Asic...

This one is a PAL-I SMS 2 M4Jr. PAL 2M revision board... Most NTSC boards, even have the jumpers already labeled there, while this one in the other hand doesn't, not a single trace..

**Ace** · 03-09-2009, 10:04 PM

Could you take a close-up picture of that Master System II's motherboard? I may have a fix for you.

**TmEE** · 03-09-2009, 10:46 PM

http://www.hot.ee/tmeeco/SMS_F.JPG

My SMS2, same model as your troublemaker...

**Ace** · 03-09-2009, 10:58 PM

That's it! That's the mod I had seen performed on that motherboard!

My Master System II has an IC BD M4Jr. VA1(or similarly-numbered) motherboard, which actually has a spot with a jumper to toggle between NTSC and PAL, with a piece of metal soldered between the common point and the NTSC setting.

But, damn it, I would have loved to have that Sonic BIOS in my Master System II. How many Megabits is the BIOS ROM anyways?

By the way, did you see a solder spot under the RF unit for a MegaDrive Model 1-style 8-pin DIN multi-A/V out? When I took apart my Master System II to clean out the insides(was quite dusty in there), I saw the solder spot under the RF unit.

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