Adding capacitors to video cables?

[Fizzycapola]

About 17 years ago a friend of mine bought a games console from an amateur electronics enthusiast. The lead that came with it (RGB SCART) had been modified (on the end that goes into the TV) with capacitors soldered to the pins inside. I wonder what is the purpose in this, from what I remember the picture quality was pretty good and vibrant using the lead compared to others.

[gonzo0815]

Re: Adding capacitors to video cables?

How those caps where conected? Usually there are two reasons to put caps on cables: to isolate the cables galvanically, to avoid hum or ground loops (you have to cut the wire and bridge them with the cap)
Or to short certain AC frequencies to ground, depending on the value (the lower, the higher the frequency wich is shorted) in soldering the caps from the signal wire to ground.

[Fizzycapola]

Re: Adding capacitors to video cables?

Well I have no idea whatsoever about this. All I know is the picture & sound quality from the lead (RGB SCART 21 pin) was legendary compared to normal leads without capacitors in, it may have had other components inside too, it's all long long ago now though it only exists in me and my friend memories.

[starfury1]

Re: Adding capacitors to video cables?

sort of vaguely remembered something about that but anyway did a search

it basically tweaking the video sig RGB (chroma) whatever, according to this site by boosting?

from this thread I found here

The original mod link is dead.

So you will have to search for it if you want it

heres another link

this one talking about removal of caps with different consoles, and other stuff

Yet to find a good technical explanation link of it all

Like Gonzo0815 technical answer above.

As soon as you have a capacitor and some resistance you got a filter of some kind,
just depends on it and what you are feeding it to the results you get at the output
(Gonzo0815 has more or less said this above)

I have a funny feeling that caps in series will cause a peak in bandwidth response
at some point so this may be why its more vibrant
but I will stand to be corrected on that....

I would say it somewhat dependent on whats feeding it circuit wise too.


Do you remember which game console it was, just out of curiosity?

Ok didn't really read this, its about modifying a sega for RGB SCART here

Looked interesting

Not the exact answer I think you were looking for but Hope it helps

Cheers

[Fizzycapola]

Re: Adding capacitors to video cables?

It was a SNES scart lead, I think oem, the end unscrewed and there were capacitors inside.

There was another SNES scart lead, more common it had capacitors and a switch for maximising the picture quality to compensate for different TV brands. (not related to 50/60hz or composite/rgb switching)

I spoke to my friend recently, he says he may be able to find this lead, but it may be sometime before he finds it. I'll post some pictures soon hopefully.

[starfury1]

Re: Adding capacitors to video cables?

Thanks
Yeah, as I said vague memory of something about it which is why the search....
(never had much to do with scart or SNES....)

As I suspected the info was going in a little different direction to what you were talking about.

Sounds interesting thought, hope your mate can find it.

Cheers

[Logistics]

Re: Adding capacitors to video cables?

That same site explains that the NTSC versions of the SNES had a DC offset on the R, G and B lines. It's standard practice to use at least 220uF caps as part of the coupling filter to remove it. The VGA box for the Dreamcast had the same thing already built into it.

[Tom41]

Re: Adding capacitors to video cables?

I've seen caps inside SCART leads before. The RGB SCART lead I had for my PSOne had caps soldered to the Red, Green and Blue signal pins for some reason. Apparently it's to adjust the black level of the picture; without the caps all black areas would appear gray.

The switch you mention on the RGB lead may just be for switching the RGB signal on and off. Most TVs with a SCART socket 'listen' for a voltage on a certain pin - if present, it puts the TV into RGB mode. If the voltage is not present, it uses composite-only mode.
That may explain why this lead provided a more vibrant picture; it was passing through the RGB switching voltage. The other leads might not have been doing that (I have one for Sega Saturn that doesn't pass it through), and therefore the picture would have been composite.

From worst to best picture quality, the connection types for games consoles are as follows:
RF - Composite - RGB SCART - Component - HDMI

[Logistics]

Re: Adding capacitors to video cables?

Actually, RGB+HV is video's native format; this cannot be bested. No matter what your display, everything has to be converted back into this format in analog form for the screen to display it. It is superior to everything.

If manufacturers included pure RGB inputs and outputs on their products, that would make Macrovision sad because it's impossible to implement copy protection over pure RGB.

[shadow]

Re: Adding capacitors to video cables?

Actually, RGB+HV is video's native format; this cannot be bested. No matter what your display, everything has to be converted back into this format in analog form for the screen to display it. It is superior to everything.

[If manufacturers included pure RGB inputs and outputs on their products, that would make Macrovision sad because it's impossible to implement copy protection over pure RGB.

Now wouldn't that be great to see!