PAL Megadrive 60hz

[butane bob]

I have found someone close to me who can perform a 60hz mod to a PAL megadrive for me but he says that it wont produce a picture when using RF or Composite and that you must use an RGB/Scart TV. Could anyone please tell me if this is true, as i thought it would be fine on my Multi system (PAL/NTSC/SECAM) television with composite, but he doesn't.

I am afraid 60Hz on a PAL megadrive will not produce a coherent picture via composite or RF - it only produces a viewable picture via RGB.

Now i would understand if it produced a black and white or Rolling picture on a PAL only television, but no picture at all?? that doesn't make sense to me
Could anyone clear this up for me? I just want a bloody pal megadrive running in 60hz without the need to go and get an RGB Scart TV

Cheers.

[phreak97]

a pal megadrive running 60hz will produce a perfectly clear black and white picture (assuming your tv supports 60hz).
you need an additional mod to produce colour at 60hz.

ps. there is already a topic here discussing exactly this, and it contains info on how to get colour at 60hz, look under the import mods section.

[butane bob]

Ok thanks , might just get a Jap megadrive then.

This is what the person also had to say about modding a pal system

It has to do with the clock used in the PAL models (particular component involved in digital to analogue conversion). I have researched a mods on various machines and I am afraid this is the case.

I'd need to transplant a clock from an NTSC megadrive. At that point you might as well get an import megadrive

Sounds kinda weird.

[phreak97]

yeah, the clock and the crystal are one and the same:)
there are speed problems with a 60hz pal machine anyway i have heard, so yeah, if you have the money, get a japanese system

[Guest]

Why bother getting a JAP Megadrive when an RGB SCART for a Megadrive is cheaper? :blink:  

[Hidden Frog]

I added a 60Hz switch into my PAL Megadrive, and you do need it to output RGB in order to get a colour image at 60Hz. Luckily I have an old Commodore 1084 monitor handy, so I just made a 9 pin RGB cable to suit the monitor (it lacks scart).

As for speed problems, there are minor glitchy things that happen with some games, mostly in the form of graphical anomalies. Some PAL games also won't work at all at 60Hz (Megalomania routinely checks the Hz mode rendering the game unplayable), most games work by switching the Hz mode after boot up, and a few even work in both PAL and NTSC modes.

I primarily modded my PAL Megadrive so I could get full screen, full speed gameplay. Nowadays I just use my softmodded Xbox and run all my old 16-bit games through emulation on it.

[phreak97]

there is a fairly simple mod for getting colour from a megadrive in 60hz.. i covered it in another post..

for NTSC colour output, the correct values are a 3.579545MHz crystal, 50pF (I used a 60pF) variable capacitor (trimmer), 15k resistor, and a 30pF capacitor. For PAL colour output, a 4.433619MHz crystal should be used instead; other values are the same.

the chip you are working on is the video encoder, it's labled CXA-1145 or CXA-1145P or something like that.

cut the trace to pin 6 before you begin, and make sure there's no trace leading to pin 5 (there shouldn't be).

Now, using good RF construction practices (keep cables as short and direct as possible, and solder as much to the board as you can), solder one end of the 30pf cap to pin 5. Solder the other end to the crystal. Solder the other end of the crystal to pin 6. Then solder the resistor from ground (pin 1, test pin 7, it might be ground and it's closer) to pin 5. Then the variable capacitor or fixed capacitor substitute from ground (pin 1) to pin 6.

turn the system on, you should get colour no matter what now. the picture may not be perfectly clear, adjust the variable capacitor (carefully) untill you get a clear picture.

keep in mind, that the colour format you choose will be active whether you are in 50Hz or 60Hz (eg. if you choose ntsc, you will have the choices of ntsc50 or ntsc60). if you want dual format, youll have to install a switch to choose which crystal you want, but i wouldnt be suprised if having the wires running to a switch would degrade the quality. having said that, the video encoder is fairly close to the outside of the board if i remember, so you might be able to have the switch quite close.

it sounds alot of crap, but it's only four components if you want one video format.. you can make the whole thing on a bit of perf board cut to 4 holes by 6 holes and have only three wires coming off it.

[butane bob]

Why bother getting a JAP Megadrive when an RGB SCART for a Megadrive is cheaper?

Possibly because then you have to first locate and second fork out for an rgb monitor or scart compatible television, which in Aus isnt that easy...