RGB megadrive cable thoughts

[simonbelmont2]

My RGB cable was created with informations from this page: http://www.mmmonkey.co.uk/console/sega/ms-md-scart.htm.
Today I find another page with another schematic for the RGB megadrive cable: http://members.optushome.com.au/eviltim/gamescart/megamstr.png
The only differences are :
- my cable have no capacitors;
- my cable resistor is 100Ω not 180Ω.
Does anybody know for what are used this capacitors? It's something wrong if I don't put this capacitors? What about the resistor?

Thanks!

[Jamtex]

The caps strip the tiny ammount of DC voltage that is present on Megadrives, some TVs will require it and some will not and 75ohm resistors will be fine. You could try both to see what looks better.

The resistor on pin 16 is to drop 5V to about 3V, as the SCART standard is for 1 to 3 volts, it's not critical to use an exact resistor. I use 100 ohm resistors as it works...

[simonbelmont2]

Thanks Jamtex for your quick response :D. Another question I have: If I don't put the resistor 100 ohm (pin 8 to pin 16) it can damage something?

[Jamtex]

It probably won't damage anything but it's a good idea to have so that the voltage is dropped to the SCART standard. On the Saturn RGB scart lead I've had to remove the resistor to get the TV to switch to RGB mode.

[simonbelmont2]

From what I've read now on wikipedia about the scart the schematic is something like this:

- Pin 8 (status and aspect ratio) have 3 states:
0–0.4V - OFF
5–8V - 16:9
9.5-12V - ON/4:3

- Pin 16 (blanking signal or rgb selection) have 2 states:
0–0.4V - composite
1–3V - RGB

So if this is the right schematic I think will don't damage anything. I can manualy change to RGB from my remote control.
My conclusion is if you put the resistor (in my case 100 ohm) to pin 8 and pin 16 the aspect ratio and video signal will be change in 16:9 and RGB.
Anyway thanks for your response.

[Jamtex]

Some TVs require a voltage on Pin 8 or they will not switch to AV mode and some TVs require a voltage on Pin 16 or they will not display RGB but you'll get a picture as you'll get Composite video. On TVs where you can manual switch you could get away with not having anything on pins 8 or 16.

However as most games consoles do only have 5V some TVs will go into 16:9 (widescreen mode), which is funny when you have a Sony Playstation 2 with an official RGB Scart Lead going into a Sony portable TV and it defaults to widescreen...

[simonbelmont2]

You have right but if you have an TV (Teletech is the name of my TV) just like mine you can manualy change the aspect ratio to AUTO; 16:9 and 4:3 or change the video signals to AV 1; AV 2; F-AV; RGB and S-VIDEO :D.

[TmEE]

I usually leave the Pin8 unconnected since I can live without autoswitch and I do not like my stuff showing up in widescreen.