A1200 Problem with image, RGB scart [UNSOLVED]

trydowave · 12 December 2015, 00:52

Hi. I have an A1200 and A500 running to my Sony Trinitron and Sony BVM.

The A500s picture is beautifully clear while the A1200 (when the brightness and contrast are turned up) has distortions. For example if there is white text on a black background there will be a dark black bank running parallel with the text on a slightly greyer black background. Also there's a band of interference that travels up the screen slowly?

Ive changed over the Amgia RGB Video out to scart cables so its definitely something to do with the A1200.

Video: [ Show youtube player ]

Pics:

Does anyone know why this is happening and what I can do about it?

Thanks
Tony

TjLaZer · 19 December 2015, 22:21

Can you please explain how you solved it?

trydowave · 22 December 2015, 11:53

I thought I did but I was wrong. The lines are more pronounced when there's a black background and white text. Ive turned the contrast up to max here, it's hardly noticeable normally but when you're hooking it up to a Sony BVM you want it to look amazing!
The same problem occurred with my consumer Sony TV. The A1200s output is the same using two different video cables. When I hook up my A500 using the either cable the picture is perfect!
I think the problem lies somewhere in the A1200.

Ill have to take it in for repair at some point. Ill have to give Mutant Caterpillar a call as they fixed my A600.

demolition · 22 December 2015, 13:01

I think the picture is generally different on 1200s. The blacks on my 1200s are not completely black while they are on my 500 and 600, so somehow there is a quality difference. I don't see the issue you're seeing though.

Daedalus · 25 December 2015, 16:56

It could always be that go-to issue of capacitors failing somewhere in your video circuitry. It appears you've done all the likely troubleshooting steps so maybe get them looked at.

Stedy · 27 December 2015, 17:15

Hi,

Try AC coupling the RGB video from the Amiga. Add 220uF capacitors in series with the RGB signals. It might be the fact that black level from the Amiga is 600mV, not 0V. I saw something similar a few years ago (non-Amiga related) and seem to remember that as the cause.

Why are you trying 100% brightness?

Not sure what is causing the rolling bands through the video though.

12 December 2015, 00:52	#1
trydowave Registered User Join Date: Jan 2010 Location: N/A Posts: 873	A1200 Problem with image, RGB scart [UNSOLVED] Hi. I have an A1200 and A500 running to my Sony Trinitron and Sony BVM. The A500s picture is beautifully clear while the A1200 (when the brightness and contrast are turned up) has distortions. For example if there is white text on a black background there will be a dark black bank running parallel with the text on a slightly greyer black background. Also there's a band of interference that travels up the screen slowly? Ive changed over the Amgia RGB Video out to scart cables so its definitely something to do with the A1200. Video: [ Show youtube player ] Pics: Does anyone know why this is happening and what I can do about it? Thanks Tony Last edited by trydowave; 22 December 2015 at 11:41.

22 December 2015, 11:53	#3
trydowave Registered User Join Date: Jan 2010 Location: N/A Posts: 873	I thought I did but I was wrong. The lines are more pronounced when there's a black background and white text. Ive turned the contrast up to max here, it's hardly noticeable normally but when you're hooking it up to a Sony BVM you want it to look amazing! The same problem occurred with my consumer Sony TV. The A1200s output is the same using two different video cables. When I hook up my A500 using the either cable the picture is perfect! I think the problem lies somewhere in the A1200. Ill have to take it in for repair at some point. Ill have to give Mutant Caterpillar a call as they fixed my A600. Last edited by trydowave; 22 December 2015 at 12:04.

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19 December 2015, 22:21	#2
TjLaZer Registered User Join Date: Sep 2004 Location: Tacoma, WA USA Age: 52 Posts: 1,915	Can you please explain how you solved it?

22 December 2015, 13:01	#4
demolition Unregistered User Join Date: Sep 2012 Location: Copenhagen / DK Age: 43 Posts: 4,190	I think the picture is generally different on 1200s. The blacks on my 1200s are not completely black while they are on my 500 and 600, so somehow there is a quality difference. I don't see the issue you're seeing though.

25 December 2015, 16:56	#5
Daedalus Registered User Join Date: Jun 2009 Location: Dublin, then Glasgow Posts: 6,334	It could always be that go-to issue of capacitors failing somewhere in your video circuitry. It appears you've done all the likely troubleshooting steps so maybe get them looked at.

27 December 2015, 17:15	#6
Stedy Registered User Join Date: Jan 2008 Location: United Kingdom Age: 46 Posts: 733	Hi, Try AC coupling the RGB video from the Amiga. Add 220uF capacitors in series with the RGB signals. It might be the fact that black level from the Amiga is 600mV, not 0V. I saw something similar a few years ago (non-Amiga related) and seem to remember that as the cause. Why are you trying 100% brightness? Not sure what is causing the rolling bands through the video though.

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