asain pal mega drive,possible to get colour picture on a Divers 2000 tv ?

[bigsanta]

Managed to get lucky and win a dreamcast Divers 2000 CX-1,here's one of the photo's i took http://img56.imageshack.us/img56/391/ntscukoi6.jpg .

And as i'd like to  connect this asain pal50 mega drive to it (which is modded with the language and 50/60 hz switches ),albeit with a composite lead,which is the only decent input available on the Divers tv ,but at the moment, the console's picture comes through in black and white.

This also happens with a ps2,but if i use free mcboot /or ULE and change the pal ps2 to  ntsc mode, i get a normal colour picture through the same composite lead,so why will this asian pal 50 mega drive not do the same,when it's switched over to 60hz.


fraser

[Tiido Priimägi]

That is because the color carrier freq gets changed when you switch between 50 and 60Hz on MD... only way is to add a fixed clock to the RGB encoder chip (~4.3MHz for PAL, ~3.5MHz for NTSC).

[l_oliveira]

MD requires an oscillator box of 15 times the color carrier frequency. For NTSC it's 53.6393175  MHZ. Pretty standard (same crystal used on the Playstation GPU)

You can also bypass that, cut the clock output from the VDP and put a 3.579545 MHZ crystal directly on the CXA1145 pins but then you would get a not so nice color carrier artifact on the image.

[viletim]

The colour subcarrier should be drived from the same source as the pixel clock (or at least phase locked to it) else, as l_oliveira says, it won't look so good.

Both PAL and NTSC consoles use the same master oscillator frequency so the best bet is some kind of programmable frequency divider circuit.

[Tiido Priimägi]

Master clock on PAL and NTSC machines is not same... my EU MD2 has a 53.203424MHz clock and Nomads have 53.639317MHz clocks...
The NTSC master clock would fix the problem with that monitor but would give you black and white on your TV... I did this in my MD2 : http://www.hot.ee/tmeeco/MYSMD2.JPG
No trouble at all in this configuration

[albino_vulpix]

You love showing that thing off don't you :p

You can also bypass that, cut the clock output from the VDP and put a 3.579545 MHZ crystal directly on the CXA1145 pins but then you would get a not so nice color carrier artifact on the image.

What kind of artifacts are we talking here? Any pics/examples?

[Tiido Priimägi]

Instead of the regular Sega lines, you get them moving around I believe... ?

[phreak97]

i've got a pal megadrive modded like that, straight into the cxa1145. if i remember ill take some pics tomorrow. it's nothing major, theres just a bit of extra fuzzy crap round the edges of stuff, i've seen worse from the ps2's stock composite video output tbh.

[l_oliveira]

Instead of the regular Sega lines, you get them moving around I believe... ?

Exactly and here in Brazil (3.575611MHZ) it moves from left to right, slowly.

[phreak97]

i dont remember those lines, but it's been a long time since i used that megadrive, i have a genesis aswel as another megadrive now, so i use the right console for the game these days.