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sestrenexsis
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Slight interference on video output after PSU replaced

by sestrenexsis Tue Feb 06, 2018 2:40 pm

Hi there,
some time ago I had an issue where my Saturn's PSU died and I had to buy an off-the-shelf one to solve it, since replacements are very hard to come by where I live.
Here's that topic: http://www.racketboy.com/forum/viewtopic.php?f=1&t=51833

Fortunately, that issue has been solved, but now I'm noticing another (minor) issue.

To summarize, I have a VA9 PAL Model 2 Saturn, and I've been using the same RGB SCART cable forever. After solving the problem I mentioned, I started noticing a loss in video quality. Previously, the console used to output razor sharp images no matter the display. But now the image is slightly worse. The effect is different depending on the display:
CRT: Quality is decent, but if you look up close, especially in dark areas, you can clearly see the background artifacts. I know for a fact these artifacts do not come from the CRT. Here's a video of it, pay attention to when the screen goes black:
https://www.youtube.com/watch?v=tk5zeAPgukE

HDTV: Less artifacts, but looks seriously downgraded. Almost like composite or RF. My phone had a hard time trying to capture it on video, so here's a picture up close. See how the text looks blurred and has that kind of chromatic aberration similar to composite signals. (Mind you, the picture is not blurred, that's exactly what the console outputs.)
Image

So, should I just stop caring? If not, how can I "clean up" the video output?
Thanks in advance :mrgreen:
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marurun
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Re: Slight interference on video output after PSU replaced

by marurun Tue Feb 06, 2018 3:19 pm

Sounds like the PSU is not providing clean enough power to the system. You could probably replace some of the caps on the power line going to the video encoder with higher capacity ones, but it might be better to go back and see if you can't do more to clean up the power coming off the PSU to the rest of the system, in case other issues might also crop up.
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sestrenexsis
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Re: Slight interference on video output after PSU replaced

by sestrenexsis Tue Feb 06, 2018 5:07 pm

marurun wrote:Sounds like the PSU is not providing clean enough power to the system. You could probably replace some of the caps on the power line going to the video encoder with higher capacity ones, but it might be better to go back and see if you can't do more to clean up the power coming off the PSU to the rest of the system, in case other issues might also crop up.


Yeah I'm pretty sure that must be the issue. As for replacing caps, the PSU I bought is still under warranty, so I don't think I'll touch that.
If you read the previous topic where we were discussing the dead power supply and all that, you might've noticed I mentioned at one point that I stripped the original PSU board of all the components. Maybe I could reuse the caps from the original board?
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marurun
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Re: Slight interference on video output after PSU replaced

by marurun Tue Feb 06, 2018 5:51 pm

I would suggest rigging up a cleaner board to go between the PSU and your Saturn. I don't know what size or rating caps you'd need, but you will need some. I do remember your other thread, and I think if you can clean up the power before it enters the Saturn you won't need to specifically clean the power to the video encoder.
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sestrenexsis
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Re: Slight interference on video output after PSU replaced

by sestrenexsis Wed Feb 07, 2018 11:22 am

marurun wrote:I would suggest rigging up a cleaner board to go between the PSU and your Saturn. I don't know what size or rating caps you'd need, but you will need some. I do remember your other thread, and I think if you can clean up the power before it enters the Saturn you won't need to specifically clean the power to the video encoder.


I think I might be able to do that with some help. I don't have an oscilloscope though, so I'll have to do lots of trial and error.
As for what caps to use, I honestly have no clue. Does anyone have any suggestions?
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Re: Slight interference on video output after PSU replaced

by zyrobs Sat Feb 17, 2018 2:42 pm

The 9V pin on PAL Model 2 saturns (it is actually 12V there) is used to provide voltage for the SCART cables RGB Switch pin. In the absence of that pin in the power supply, the SCART cable will have no voltage on that specific pin, and so your television will not switch to RGB mode and instead use composite video.

The official first party cables use the 9/12V pin of the power supply.
Third party cables can use the 5V pins instead, but if you use those, the TV switches to 16:9 on powerup (9-12V on the Status pin of the SCART cable means 4:3 signal, 5-8V means 16:9 signal, 0-2V means no auto switching).
Also note that NTSC units only have 5V in the a/v out, this was a change introduced in PAL boards.
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Re: Slight interference on video output after PSU replaced

by sestrenexsis Wed Feb 21, 2018 1:54 pm

zyrobs wrote:The 9V pin on PAL Model 2 saturns (it is actually 12V there) is used to provide voltage for the SCART cables RGB Switch pin. In the absence of that pin in the power supply, the SCART cable will have no voltage on that specific pin, and so your television will not switch to RGB mode and instead use composite video.

The official first party cables use the 9/12V pin of the power supply.
Third party cables can use the 5V pins instead, but if you use those, the TV switches to 16:9 on powerup (9-12V on the Status pin of the SCART cable means 4:3 signal, 5-8V means 16:9 signal, 0-2V means no auto switching).
Also note that NTSC units only have 5V in the a/v out, this was a change introduced in PAL boards.


First of all, sorry for the pretty late reply.

This is actually the information I was trying to track down for a while. How the Saturn handles RGB/Composite switching. But since generic articles about SCART don't seem to help, I was kinda stuck.
And actually, it's not 12V on PAL, but 9. At least that's what the original PSU board says.
As for the 16:9 thing, to be honest I don't really think it's an issue, because the CRT I'm using has a force aspect ratio function. So I can change back and forth if I need it.
In that case, my solution would be to buy a third party SCART cable and be done with it. To be fair I don't want to buy another power supply just to get the 9V going.

However, if my Saturn really is outputting composite, then this is extremely weird:
When I use an adapter with the console (namely SCART to RCA/S-Video) it won't work. At least not properly. (I know it's not the adapter, it works everywhere else.)

This is what happens when adapting to RCA:
https://www.youtube.com/watch?v=er2vfK4Q3R0
And with S-Video it gets slightly more interesting, displaying sort of like a negative-looking picture:
https://www.youtube.com/watch?v=ccAXFrXPJdA

Could there be something about the video display getting messed up? I don't know at this point. Like this, using any capture cards would be useless if I planned to.
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