A1200 Scart Cable - Colour not right on the TV

[bob808]

I purchased an RGB Scart lead for my A1200, and on its arrival eagerly set it up...
I can get a picture on my TV, and sound works fine, but the picture is a bit washed out and the colour is not vivid. I can make it a bit more useable by turning the contrast right up, and the brightness too, but this is not ideal.
Should I have setup the Amiga as if I am using a monitor? I had been using a 3.1 install just setup to work with the RF out until now, so could it just be that I need to tell the amiga I am using a monitor & if so what one? Or might it be an issue with any of my kit?

Thanks

bob808

[Toni Wilen]

I guess your TV is only using composite video from the Scart socket instead of being in RGB-mode. Correct AV-channel? Can you try other TV?

[adgloride]

Have you got one of those scart plugs were you can connect about 3 different scart cables up to the tv? I've found these can sometimes cause problems with the colour.

[bob808]

Toni - The scart should be ok with RGB - At the moment I do not have access to another TV to check as my 2nd set has just been scrapped and I am awaiting the replacement.

adgloride - I plugged straight into the tv, not using any splitters or anything.


I guess I will see if I can get it round to a friends and test on their telly - will post back with some results when I get them.


bob808

[DDNI]

want to build one of these cables, is there an A1200 RGB to SCART schematic.

[bob808]

Originally Posted by DDNI

want to build one of these cables, is there an A1200 RGB to SCART schematic.

There are schematics around (I will see if I can find them in my internet cache and post) but I took the easy option and payed £8 for one on ebay

[alexh]

Originally Posted by Toni Wilen

I guess your TV is only using composite video from the Scart socket instead of being in RGB-mode.

AFAIK there is no composite video output on the 23-pin Amiga video connector and so what you suggest cannot happen. Either it works and you get an RGB picture or you dont get anything.

Check inside the connectors (SCART & 23-pin) for resistors if there are any connected to the RGB lines, remove them.

Originally Posted by alexh

AFAIK there is no composite video output on the 23-pin Amiga video connector and so what you suggest cannot happen. Either it works and you get an RGB picture or you dont get anything.

There is a so called "Composite Sync" signal on the 23-pin Amiga video connector. If a television does not support RGB it picks up the "Composite Sync" as composite video and displays a black and white picture. So it will display something even if there is no RGB support in the TV.

When a TV displays the RGB signal from the 23-pin Amiga video connector, it uses the Analog Red, Analog Green, Analog Blue AND Composite Sync signals to build up the picture. The video connector also has a Horizontal Sync and Vertical Sync signal which is used for monitors with a 9-pin RGB connector.

Look up Hardwarebook on google. Under "Connectors" you will be able to find the pinouts of the Amiga video connector and Scart. You can also find the video connector pinouts in a lot of original Amiga manuals, for example the Amiga 500 owners manual.

Here is some advice how to build a 23-pin Amiga video connector to Scart RGB adapter. Connect the following:

RGB:
Amiga Pin 3(Analog Red) to Scart Pin 15 (RGB Red In)
Amiga Pin 4(Analog Green) to Scart Pin 11 (RGB Green In)
Amiga Pin 5(Analog Blue) to Scart Pin 7 (RGB Blue In)

RGB GND:
Amiga Pin 16(Video Ground) to Scart Pin 13 (RGB Red Ground)
Amiga Pin 17(Video Ground) to Scart Pin 9 (RGB Green Ground)
Amiga Pin 18(Video Ground) to Scart Pin 5 (RGB Blue Ground)
(Note that Pins 16-20 on the Amiga are all "Video Ground", so you don't have to use 16, 17 and 18 as I wrote above, you could also use just one pin or some other combination of 16-20)

Composite Sync:
Amiga Pin 10(Composite Sync) to Scart Pin 20 (Composite Video In)

Composite GND:
Amiga Pin 19(Video Ground) to Scart Pin 17 (Composite Video Ground)
(again.. Note that Pins 16-20 on the Amiga are all "Video Ground", so you don't have to use 19 as I wrote above, you could also use some other pin from 16-20)

Also, IF you would like to have the sound from the Amiga connected to the same Scart so that your television speakers would output the Amiga audio, then you need to do the following:

Take a stereo RCA cable. Cut the connectors from the other end and strip the ends open. There are two wires inside and you need to separate them. They should not be in contact with each other! The wire that is in the middle is the one that has the audio signal(+), and the one on the outside is the signal ground(-). (I put the + and - symbols there so that everyone would understand and I'll also use it later You could ofcourse also make your own RCA cable, but just buying one and cutting it is usually cheaper, faster and easier. The RCA cord that has a RED RCA connector on the other end is the RIGHT channel. The cord that has either a BLACK or WHITE RCA connector on the other end is the LEFT channel.

RIGHT channel.
+ to Scart Pin 2 (Audio In Right)
- to Scart Pin 4 (Audio Ground)

LEFT channel.
+ to Scart Pin 6 (Audio In Left)
- to Scart Pin 4 (Audio Ground)

Note that signal ground(-) from both left and right are connected to the same pin on the scart connector.


If someone uses this information for making any adapters, please be sure to check that all the pins above are correct before doing anything, cause there might always be typos. Also if you end up damaging your amiga or TV or anything else or your house burns down or something else because of you following my instructions, I won't be held responsible. Following my instructions here is on your own risk!

[patrik]

@spirited:

The Amiga doesn't send any video on the composite sync pin, just the syncs, so if the TV doesn't support RGB you will get a black image.

Here is a more or less official version of an Amiga scart-cable which supplies the right voltages to pin 8 and 16, which tells the TV to switch to RGB mode. Without those, it wont work on many TVs.

[DDNI]

Originally Posted by bob808

Should I have setup the Amiga as if I am using a monitor? I had been using a 3.1 install just setup to work with the RF out until now, so could it just be that I need to tell the amiga I am using a monitor & if so what one?

Thanks for schematic. Can anyone answer the above question though?

Originally Posted by patrik

The Amiga doesn't send any video on the composite sync pin, just the syncs, so if the TV doesn't support RGB you will get a black image.

At least my Amiga 500 does, and I just tested it. My TV has 2 Scart connectors and only one of them supports RGB. When I plug the cable in to the Scart which supports RGB I get a RGB picture, and when I plug it to the other Scart I get a black and white composite picture.

Just to be sure, I hooked the Amiga 500 up to a at least 10-year old VHS VCR with my Amiga 23-pin -> Scart cable, and I got a black and white composite picture. The VHS VCR has only one Scart socket and the picture from the VCR is transfered to the TV with a RF antenna cable. There is no support for RGB in the VCR.

I have not tested this with my Amiga 1200, only with the Amiga 500, so I don't know more, maybe there is different versions..

[patrik]

@bob808:

If the image looks dark/dull compared to other input, open the dsub and scart connectors and make sure that there are no resistors mounted on the Red, Green and Blue signals - pin 3,4 and 5 on the dsub and pin 15, 11 and 7 on the scart.

Some geniuses who builds these cables does for some reason think it is a good idea to connect 75Ohm resistors in series with each of the Red, Green and Blue signals. In combination with the 75Ohm termination-resistors (tied to ground) which all TVs/monitors have for each Red, Green and Blue signal, this effectively becomes voltage dividers, making the Amiga output 0.35Vpp, instead of 0.7Vpp which the TV/monitor expects for each colour, resulting in a very dark/dull image. The composite sync signal normally also gets this treatment.

I have also seen those bobs connect the digital ground (pin 13) to video ground (pin 16-20) in the 23-pin dsub which can only give you static in the image and those should NOT be connected. And do not let me get started on the quality of the cabling they often use.. normal serial-port cable seems to be the preferred choice... heh, total crap compared to the 75 Ohm coaxial cables which the Red, Green, Blue and Sync signals should have as they are video signals.

Here you will find a good schematic for a scart-cable btw.

To get a good quality-cable, just buy a stock fully-coupled scart cable and chop one connector of - those are very cheap and as long as they arent very thin, they usually have 75 Ohm coaxial cables for the colours and the sync. This way you don't have to solder the scart side of the cable either .