A1200 RGB colours are "different"

[PowerPie5000]

Can anyone please help me figure out why my A1200 is showing washed out colours over RGB?

I recently got a replacement RGB scart lead as i lost my previous one a while ago and have noticed that the colours seem a bit dull. The worst is the colour red! if anything red is displayed it will show up as orange for some reason? (noticeably on the dreaded software failure screen).

Just out of curiosity i tried the original RF lead and the colours were nice and bright and as they should be (red is red, although poor quality picture!). I also checked the wiring in both ends of the scart lead and everything seems to be ok as far as i can tell.

Is it possible that it could be a fault developing in my amiga? or is this a common issue using RGB scart leads? any help is appreciated, thanks

[prowler]

Was it showing washed-out colours when you had your old RGB to SCART lead, or just since you got the new one?

Have you changed your TV lately? Some newer LCD-type TVs are more fussy about the RGB signals.

There is a lot of info in these forums on this subject.

Just search for 'RGB' and 'SCART'.

[PowerPie5000]

Hi, its been a while since i last used my old A1200 and i never really noticed it back then with the old scart lead. I have tried it on all 3 of my tv's and it is the same. If i use the RF lead the colours are fine but the picture is poor, and when i use the rgb scart the colours are a bit washed out and red looks more orange.

I cant figure out what it could be? maybe its best if i buy another scart lead and see if its the same but i dont see any problems with the wiring in the one i have, maybe it could be a resistor in the lead? i will have to test it when i get a chance. Just hope its not the amiga port or chip problem as its been a well looked after system

[prowler]

Originally Posted by PowerPie5000

maybe it could be a resistor in the lead?

If the resistors (there should be 3 - one each in the R, G and B signal leads) check out OK, then you may need to increase their value slightly. (From memory, the original value is 75 ohms or so. The performance might be improved by increasing this to 120 ohms.)

Have a search of the other threads and see if this is mentioned at all.

[PowerPie5000]

Ok thanks for the info as i was unsure what the original values may have been. I will test the resistors and maybe try both lower and higher values until i get the right colours. I wll have a look through the threads again and see if ive missed anything, thanks

[alexh]

Whip out the resistors and see if the colours are ok without them and that the image is not saturated

[PowerPie5000]

Ok i got round to looking at the RGB cable again and was ready to remove some resistors but they are not on the red/blue/green wires! So i guess i can scrap that idea!

I have seen some diagrams on the net for amiga scart pinouts etc... but they look quite basic compared to what ive got, mine has more wires and 2 resistors not mentioned in the guides i have seen. I will just get another scart lead and see what happens

[alexh]

If there are no resistors on the RGB wires at either end then either your TV is broken (should be easy to test with another RGB based console / STB) or the RGB port on your Amiga is broken (try a different TV).

[prowler]

Hi PowerPie5000,

Having thought a bit more about your problem, and reviewing what I have read in these forums, I am now inclined to think that the new RGB to SCART lead you have bought might be more suitable for the later LCD and plasma-type TVs than for those which you have tried it with.

If it is, I should imagine there will be several members here who would very much like to be informed of the details of such a cable, and will soon be making themselves known.

In the meantime, here are some links which should help you find some useful info.

Internal links:
~~~~~~~~~~~~~~~
http://eab.abime.net/showthread.php?t=37187
http://eab.abime.net/showthread.php?t=37795
http://eab.abime.net/showthread.php?t=40183

External links
~~~~~~~~~~~~~~
http://aminet.net/package/docs/hard/...SCART-RGBcable
http://aminet.net/package/docs/hard/SCART_2_Amiga
http://en.wikipedia.org/wiki/SCART
http://pinouts.ru/Home/Scart_pinout.shtml
http://pinouts.ru/VideoCables/AmigaScart_pinout.shtml
http://utopia.knoware.nl/users/epreb...ing/SCART.html
http://www.epanorama.net/documents/vga2rgb/scart.html
http://www.hardwarebook.info/SCART

Cheers,

prowler

[PowerPie5000]

Thanks for your help and the info links!

I have tested the cable on a 56" Hitachi plasma and it had no problems although i still thought the colours where a bit "off" but this was corrected after fiddling with various display options on the tv.

I also tested the cable on a 42" Samsung LCD and that also worked fine and looked better than on the Hitachi with stronger colours and more clarity (Hitachi plasma is a few years old now).

I plugged the lead into the scart 1 socket on both flat tv's and it switched channel automatically and looked quite clean. When testing with standard crt tv's the colours where the same for all (washed out with reds looking more like orange etc...)

When i get a bit of free time i will try and make a diagram of the pinouts in my scart cable in and post it here, (anytime soon) thanks again

[alexh]

CRT TV's would be more susceptible to having no grounds. Make sure all the gnd's are connected correctly.

[cosmicfrog]

as I read your post PowerPie5000 it sounded like you were going on the colour of the wires which may or may not be conected to the r/g/b pins on amiga side

[patrik]

There shouldn't be any resistors on the rgb lines in scart cables you use to connect the Amiga to a tv.

The Amiga already has a 0.7Vpp signal and if you put on say a 75Ohm resistor, you will in combination with the 75Ohm termination resistor on each rgb line in the tv create a voltage divider and cut it in half.

This results a in very low maximum rgb-level, forcing you to increase your tvs contrast a lot when using the amiga to match the signals from other equipment - ie. it will look very dull compared to other signals if you don't increase the contrast when using the Amiga.

This bad practise unfortunately seems very common and I think it is because the bundled scart cabling from one of the common amiga rgb-monitors was wired like this - something which was just copied without thinking.

The thing is that on a monitor it doesn't matter as you don't have any other sources to match - as long as you can increase the contrast enough to make you satisfied you are fine, but as already said - on a tv, you won't match the signal from other equipment.

This schema is correct:
click!

Also, as alexh says, it is a good idea to make sure all the grounds are connected.

[prowler]

Hi PowerPie5000,

I'm glad you got the new cable figured out!

Originally Posted by PowerPie5000

When i get a bit of free time i will try and make a diagram of the pinouts in my scart cable in and post it here, (anytime soon) thanks again

Thanks, that would be most appreciated, mate!

[Edit] Thanks also for your input, patrik.
Each time this subject has come up in these forums, somebody has made a more technically-minded contribution like this, supporting our guesswork and helping us to get the full picture (pun intended!).

[laser]

Originally Posted by prowler

If the resistors (there should be 3 - one each in the R, G and B signal leads) check out OK, then you may need to increase their value slightly. (From memory, the original value is 75 ohms or so. The performance might be improved by increasing this to 120 ohms.)

Have a search of the other threads and see if this is mentioned at all.

if the original value of the RGB resistors is 75ohms,the performance might be improved if you put a resistor of low value...not high
Low value= LOW resistance
so if the original value is a 75 ohms resistor,maybe you gain performance using a 50 ohms resistor

[prowler]

Originally Posted by laser

if the original value of the RGB resistors is 75ohms,the performance might be improved if you put a resistor of low value...not high
Low value= LOW resistance
so if the original value is a 75 ohms resistor,maybe you gain performance using a 50 ohms resistor

OK, laser, you got me!

At that point in the discussion I was relying on memory only. Can I help it if I can't remember how to activate my memory chips in the morning when I switched them off the night before?

[patrik]

Not to be a nag or anything, but as I said in my previous post, there shouldn't be any resistors there at all (on the rgb lines).

The only thing they will do is reduce the intensity of the image and make it look dull compared to everything else you connect to the telly.

[prowler]

OK, patrik, point taken.

Let's wait for PowerPie5000's schematic. He's already said no resistors "on the red/blue/green wires".

[mingle]

@PowerPie5000,

Add me to the list of interested parties when it comes to SCART cables!

I have a Samsung SyncMaster 711MP which supports RGB SCART and the 'standard' Amiga SCART cable just doesn't work...

I've applied 3V to pin 16 of the SCART cable and I get a picture, but it's jumping around all over the place!

Cheers,

Mike.

[prowler]

@All users:

girv has just posted details of the long-awaited Amiga to RGB SCART cable suitable for LCD and plasma TVs here:
http://eab.abime.net/showpost.php?p=492721&postcount=11

This is the real deal!