PAL GameCube RGB + Bandridge 7725 = Rolling Diagonal Bars

[ASDR]

Hi all,

I have a PAL GameCube hooked up over SCART RGB. When I connect it directly to my TV, all is good. When I connect it through my Bandridge 7725 passive SCART switcher I get rolling diagonal lines, mostly on bright colors, especially red. The switch seems to work fine otherwise, i.e. my N64 & Saturn don't show the slightest problems and I also did the mod to fix the power issues on the 5th input.

I was using a cheap SCART RGB cable and upgraded to a higher quality one from RetroGamingCables.uk. This improved the situation a but, but didn't fix it either. I noticed that turning up the noise reduction in my TV's picture settings to Med/High nearly completely eliminates the artifact.

Not sure what to do here. The GC and Bandridge work absolutely fine with all other devices, just not in combination. I suspect this is a sync issue and my TV has a filtering feature that fixes it 90%. No GC outputs CSYNC and the PAL GC I'm using has no S-Video, so Sync-on-Luma is not an option either. Naturally, I'm using a composite sync cable. The only upgrade I can think of is to use an external sync stripper or cable, not sure if that'll help.

Any ideas?

Thanks!

[FoxMontage]

I'm having the same problem with the diagonal scrolling lines. I believe that they are as a result of crosstalk/interference with the composite video being used as sync. I managed to get an improvement in my setup by using scart cable with individually shielded wires cable. This didn't fully eliminate the problem though.

I don't know what signal is being introduced to disrupt the sync (or whether it's that the composite video is interfering with something else), but perhaps someone else can chime in with some knowledge on the subject. Perhaps there is some coupling going on within the switch which disrupts the composite video being used as sync? Traces/wires being too close together etc.

My first step would be to try a SCART cable where all the of conductors have individual shields.

I'd be interested to hear if you have made any progress on this. Cheers.

[Guspaz]

The gamecube is using composite video sync, and the standard RGC cable does not have individually shielded lines, so there's still a chance for it to couple in. You'd want a cable with individually shielded lines, or multicore coax, like RGC's "packapunch cable", or RGA's equivalent.

At the same time, you'd also want whatever cable is on the output of the switch to be similarly shielded, and since that's the manual bandridge switch, make sure to do that internal mod where you cut that trace to fix the interference issue.

[RGB0b]

Actually, I've heard some people say that they get this interference on the Bandridge switches, even with fully-shielded cables. A few people reported that the cvbs interference was actually happening on the switch, not in the cables. I don't have one to test though.

[ASDR]

So, I finally got around to fixing this.

Like most people here I suspected the sync-over-composite to be the culprit. I have 4 consoles with csync, 1 with sync-on-luma and the GC as the sole sync-over-composite. Only one of those has issues. I ordered fully shielded cables to hook up my GC and switch. Swapping the existing SCART cable (which at least looked very high quality) for Switch<->TV with the shielded one makes no difference. Switching the GC cable for a fully shielded one makes a big difference. Or rather the sync stripper in the SCART head makes the difference. Since the GC looks fine directly hooked up to the TV there's no composite to RGB interference in the actual GC cable. Like Bob said, it's likely that the interference happens inside the switch.

Lesson learned. At under 25EUR the Bandridge 7725 is a real bargain of a 5:1 switch with no image degradation, provided you keep composite video away from it. Get a sync stripper for those few consoles that absolutely can't do anything but sync-over-composite.