Electronic – SCART to VGA adapter – green picture


I want to connect my DVD player which has a SCART output to a computer LCD monitor with VGA input. The DVD player supports the Progressive scan mode. It supports both PAL and NTSC.

I've built this adapter and it "works":

enter image description here

In PAL mode, the monitor is showing 800 x 600 @ 50 Hz and in NTSC 640 x 480 @ 60 Hz.

Only one problem: the image is greenish. First I thought I miss-connected or didn't connect R and B signals, but if I look at the picture it has red and blue colors too. White picture appears green. Red and blue appear darker than normal. There is a green tint over the picture.

One thing I noticed: the whole signal is transmitted via the green wire. I can disconnect all, if I leave green and ground connected I get picture. The two transistor circuit appears to have no use at all because it works the same without it (as long as I provide R, G, B). This makes me believe that the green signal is also carrying sync data (sync-on-green).

I've tried adding potentiometers, capacitors over green signal but with no luck. The picture disappeared. I've tried all possible settings on my DVD player. It only works with progressive scan enabled.

UPDATE: I guess I found the cause on http://www.curtpalme.com/CRTPrimer_17.shtm:

If you connect a component signal to an RGB input, you’ll only get a green image. The R and B output will be very low.

It is exactly what @DoxyLover said.

What can I do to make the green color less intense? Will a simple transistor voltage amplifier for the Red and Blue channels solve things?

Best Answer

This might come a little late, but you need to boost red and blue, not lower green, because apparently you're outputting component (YPbPr) and not RGB. You can use an amp to do that like the Texas Instruments THS7314 (I think you can order that stuff from AliExpress, not sure though) or you can use a method that may be unsafe, but it works, that is using 220uF capacitors on the red and blue signals. I used those capacitors when doing a component mod to a Super Nintendo some time ago and so far no TV has died or exploded, so I guess it's safe enough.

One question though, that has me quite curious. You managed to separate the sync signal into H and V for VGA or your monitor supports composite sync?