Dodgy Megadrive RGB cable

[Dzerp]

Hi,

I've got an official RGB cable for Master System 1/Mega Drive 1,
but, unfortunately it doesn't work :(.

It seems the composite sync is shot. I can only get a very faint composite image out if it and if I try the RGB mode it loses sync immediately.

However it seems to contain A LOT of components. Much more than you would expect from a RGB cable. A whole circuit board of them in fact. I don't understand how it works. Could anyone halp? I'd like to get the composite sync running again.

Here is what it looks like. It's in a box attached to the cable

The connectors on the left side are:

GND
VCC
+
G
R
B
Sinc
sound

Anyone have any idea what it does?

[duo_r]

is this RGB scart? I know in the scart cable there is resistors and caps for each RGB line. But I have no idea what the IC is doing on there and the transistors. Looks like it is amping the RGB circuit as well which I didn't think was necessary. At least it isn't necessary on my setup.

[Dzerp]

is this RGB scart? I know in the scart cable there is resistors and caps for each RGB line. But I have no idea what the IC is doing on there and the transistors. Looks like it is amping the RGB circuit as well which I didn't think was necessary. At least it isn't necessary on my setup.

Yea, it's a SCART cable. The IC is a TL497ACN Switching Voltage Regulator if that is any help

[ooXxXoo]

Yea, it's a SCART cable. The IC is a TL497ACN Switching Voltage Regulator if that is any help

Are you connecting this RGB cable to a 50Hz or 60Hz Tv/monitor?....It should be able to switch between 5V and 12V for the csync, but apparently is not doing it...
....
....

[duo_r]

u sure u aren't using a japanese Scart cable? Different from the UK version (and not compatible)?

[Dzerp]

Are you connecting this RGB cable to a 50Hz or 60Hz Tv/monitor?....It should be able to switch between 5V and 12V for the csync, but apparently is not doing it...


To a TV. It works with both 50 and 60Hz.




u sure u aren't using a japanese Scart cable? Different from the UK version (and not compatible)?

It seems to be French actually :S. It says "Adapteur RVB".


So I did some snooping around on the net. Apparently the Voltage Regulator is there because the Mega/MS doesn't have a 12V line which is needed(?) for automatic SCART switching.

I also found some guy who had the same problem with the same cable. So this + French origin leads me to think that there is some incompatible Frenchiness in the cable.

But anyway what works is:
Sound, auto-switching, RGB (for a second before it realizes it's out of sync)
Ie. anything but composite.

So I was thinking. Would it be possible to just solder a line from composite in to composite out on the board to bypass any weirdness it does to the signal?

[Dzerp]

Whoa, it worked!

So here is what needs to be done if anyone else has the same problem with a Model 3085 Sega RGB cable.

Cut the (+) connector one the left side of the board and connect it to the SINC on the other side (also cut).

And presto. Have a really nice RGB picture.

I'm not sure why the composite was screwed up and if it is some kind of French Secam standard peculiarity. But bypassing the circuit board did the trick.

Here is a pic

take care