Question about interference issues (RGB related)

hidefan · Post by **hidefan** » Thu Jun 05, 2008 3:36 am

Hi guys, I have a question maybe some of you could help me with. I'm using a Scart RGB to component converter (Keene) to get RGB out of my Japanese Saturn, but I'm having some problems. All text has a greenish halo around it, almost like it's all outlined in green. There is also a hum or buzzing sound coming from the tv. Could this be caused by interference with some other electronic device? It almost looks like really bad composite video.. but the cable is Euro standard and says RGB on the box. Could it be that the transcoder is getting both RGB and composite signals? I checked the pin layout against an official Euro Dreamcast Scart cable (which works fine) and the Saturn one has more pins connected. Any help is appreciated

it290 · Post by **it290** » Thu Jun 05, 2008 5:26 am

Sounds like a grounding problem. Make sure the ground is properly connected. IIRC on the Saturn the ground is carried on the outer shell of the connector, so ensure that it's fitting into the console correctly.

phasecactus · Post by **phasecactus** » Thu Jun 05, 2008 6:25 am

wikipedia wrote:A common problem is that a TV outputs a composite video signal from its internal tuner, and this is induced or cross-talked onto an incoming video signal due to inadequate or non-existent screening on a cheap SCART cable; the result is ghostly images or shimmering superimposed on the incoming signal. To non-destructively verify if a SCART cable uses coax cables, one can unscrew the strain relief at the SCART connector and fold open the plastic shell.

Although using higher-quality cables might help in reducing a 'ghosting' effect, a more permanent method is to remove pin 19 from the SCART plug that is put into the TV. Pin 19 is Video Out, and removing it prevents a signal from being broadcast by the TV into the cable in the first place, so it cannot cross-talk with the incoming signal.

hidefan · Post by **hidefan** » Thu Jun 05, 2008 6:39 am

Thanks for the replies

I'll make sure that it's properly connected as soon as can. I probably should have mentioned that I'm in the US (in Colorado, no less), and using an HDTV. phasecactus, does that info still apply to non-European TV's? I'm not sure if they are different or not..

phasecactus · Post by **phasecactus** » Thu Jun 05, 2008 7:06 am

It applies to all SCART connections, since the bi-directionality is part of the SCART standard itself.

it290 · Post by **it290** » Thu Jun 05, 2008 7:10 am

That's true for a regular SCART cable, but in the case of the Saturn cable, the video out pin should already be disconnected; there's nothing for it to connect to. The pin might be physically present but I'm sure if you open up the plug you'll see that there's no wire there. It also shouldn't be connected inside the converter because the converter itself is unidirectional. I think you can safely rule out crosstalk in this case.

Inadequate grounding will result in a blurry image and/or a buzzing noise coming out of the speakers, because the audio needs to be grounded too, and typically all of the ground pins are connected to a common ground.

hidefan · Post by **hidefan** » Thu Jun 05, 2008 7:22 pm

Well, I made sure that everything was connected securely, but no luck.. And pin 19 isn't connected

I compared the Dreamcast cable to the Saturn one, and according to the scart pinout diagram, it seems that the Saturn one has three extra pins: 4 Audio Ground, 17 Video Ground, and 18 Blanking Ground. I thought the audio ground and video ground were essential, but why doesn't the Dreamcast cable have them? Is it just a difference between how each console works? Or could one of these be causing the problem? Once again, thanks in advance for any help

Edit: Sorry, the Saturn cable DOESN'T have 4 audio ground connected, but it has 17 and 18

it290 · Post by **it290** » Fri Jun 06, 2008 2:19 am

By 'has the pins' do you mean the just the connector itself, or that they're actually connected? In my experience with consoles I have usually only had to connect the outer shell ('pin 21') to the ground pin on the console end. Try this: get a length of insulated wire the same long enough to reach from your Saturn to the keene box. Stick one end in the little notch on the Saturn AV port (with the SCART cable plugged in), and have the other one make contact with the outer shell of the SCART end, with the console on. Does that clear anything up?

hidefan · Post by **hidefan** » Fri Jun 06, 2008 3:16 am

Sorry for the confusion, pins 17 and 18 aren't connected together, they just each have wires connected to them. I don't have any insulated wiring laying around, so I'll have to wait to try that. If it is a problem with the grounding, would buying a different cable possibly solve it? I'm afraid I just don't know enough about this stuff, and buying a different cable would probably be easier

it290 · Post by **it290** » Fri Jun 06, 2008 5:42 am

Buying a different cable isn't really a solution, you'd be likely to have the same problem. The wire thing was just a test, a quick way to hook up the ground without having to do any soldering. Another thing you can do is open up the SCART end of the cable -- just unscrew the strain relief and then pop open the connector (it should just snap open) -- and check to see if there are wires connected to any of the above mentioned ground pins (including the outer shell).

hidefan · Post by **hidefan** » Sat Jun 07, 2008 2:01 am

I went ahead and opened up the scart end of the cable, and pins 17 and 18 do have wires connected to them. There's also a small wire connecting pins 17 and 18 together.. when you say outer shell, do you mean the plastic shell, or the metal casing that's inside the plastic? As far as I could tell, there are no wires connected to either the plastic or metal.

it290 · Post by **it290** » Sat Jun 07, 2008 4:24 pm

The metal casing. I would try connecting 17 and 18 to said casing.

hidefan · Post by **hidefan** » Sat Jun 07, 2008 11:42 pm

Ok, I'll try that as soon as I can. To do that, I would just solder a wire to anywhere on the metal casing?
I'm getting the feeling that after that, there aren't many other options left, so I'll stop bothering you about it

Thanks again for all of the help

it290 · Post by **it290** » Mon Jun 09, 2008 12:41 am

Solder probably won't stick, but you can just have it held in place by the exterior casing -- that's what I've done in the past, anyway.