Problem with Composite sync

halfacandan · Post by **halfacandan** » Sat Apr 22, 2006 4:39 am

Hi. I rather stupidly ripped the composite sync leg off the S-RGB A BA6596F chip of my SNES2. Is there anything I can do to sort this problem? TBH I don't really know what the comp sync signal is. Is there a similar signal anywhere else on the board?

Could I perhaps get a comp sync using this circuit? If this is possible, where would I find the input signal?

I haven't been able to find a datasheet for the S-RGB A BA6596F chip so any help finding one would be great.

Thanks
Dan

Post by **marshallh** » Sat Apr 22, 2006 9:45 am

The composite sync signal is only used when you use RGB (I don't know if the snes2 supports RGB)

If you still need it, yes, you can feed the composite video signal into your lm1881 and get the sync signal.

Again, you only need this if you'll be using RGB.

halfacandan · Post by **halfacandan** » Sat Apr 22, 2006 12:54 pm

Thanks for the speedy reply.

Again, you only need this if you'll be using RGB.

Indeed I am trying to use RGB. Could you possibly tell me where I can find the composite vid signal to feed into the lm1881? I presume that it'll be somewhere around the BA6596 but I don't have a datasheet for it.

Am I correct in thinking that I can't use the composite signal going to the multi-out port as it has already been separated from the composite sync signal?

Thanks
Dan

Post by **CronoTriggerfan** » Sat Apr 22, 2006 1:00 pm

Okay, I've always wondered this, and now seems like the perfect time to ask: What is the difference between composite and RGB? What are the disadvantages/advantages of each?

halfacandan · Post by **halfacandan** » Sat Apr 22, 2006 1:54 pm

CronoTriggerfan wrote:Okay, I've always wondered this, and now seems like the perfect time to ask: What is the difference between composite and RGB? What are the disadvantages/advantages of each?

I use RGB SCART plugs for all my games consoles (thankfully RGB capable TVs are very common in Europe) and the difference over composite sources is astounding. You can really notice it in text-heavy games like final fantasy (especially with white text on dark backgrounds).

There's much less bleeding of colours into eachother and the image is less "muddy" i.e. more consistant colours and sharper edges. It may be that the large differences seen on big-screen TVs are not so prominant on 5" LCDs so I can't give you a pro/con analysis for making portables, but I'd whole-heartedly recommend RGB...there is a difference in quality and it's not just me being pretentious.

If you'd like an analogy, I'd say that an RGB picture is like an uncompressed bitmap image while composite is like a JPEG that has been compressed a little too much.

Hope this helps
Dan

PS Some people prefer the "smoother" appearance of composite pictures.

Post by **CronoTriggerfan** » Sat Apr 22, 2006 1:58 pm

Okay, thanks! I've always just wired composite. I may have to try RGB next time.

CTFan

halfacandan · Post by **halfacandan** » Sat Apr 22, 2006 2:05 pm

I should probably mention why I'm trying to get RGB out of a SNES2. Basically I want to do a comparisson between the RGB output of the original US SNES and the miniSNES as I've heard that they are of slightly different quality.

I was using this guide to add RGB to output to my SNES2 and lifted the 4 necessary legs of the chip so that I could get a better solder join to the wires. However I wasn't meant to lift the composite sync leg and while I was trying to reattach it, I must have manipluated it a bit too much

I'll know for next time...unless I can salvage the SNES2. I tried connecting it to my TV using a composite cable but the image jumped about all over the screen. I didn't think that comp-sync info was transmitted via a composite phono plug but it must be.

I ordered a couple LM1881 ICs from the National Semiconductor website (free samples

) and I've found a couple 1 microfarrad capacitors in an old cordless phone. All I need to make the circuit I linked to above is a 680k resistor and I've found them on EBAY for ~$1 so there may yet be hope.

Dan