RGB SCART problem cause?

fallenangle

Active Member
For some time (several years) there have been what appear to be a batch of faulty independent Dreamcast RGB SCART cables with AV out blocks being sold from various sources (Amazon. e-bay etc). People want these because the official DC SCART cables didn't have separate AV out. I've had to return 3 myself and I know of many others have had problems.

There are other reported issues but the main problem is usually that the cables produces a blue toned image. This isn't a loose connection thing it is definitely a defect somewhere, either in the cabling, the DC end plug or, the SCART plug.

What is strange is that the output from the RCA sockets on the AV block work perfectly. You can connect up the (yellow) composite video to the TV and get a perfect image and likewise the L/R audio to the TV or an amp with no problem. However if you try to use the SCART plug in a non-RGB socket all you get is a very dark, faint image. Audio works fine.

I've taken the SCART plug apart and pin 20 (composite video in) looks properly wired and there's nothing wrong with the pin. So why, when the AV block video out works, doesn't it work when going through the SCART plug? Isn't the composite video output from the DC being carried on the same wire to both?

When you swap to use a RGB enabled socket everything else is OK too except you get that blue toned image. Surely this indicates a problem with the red channel (pins 13 & 15 I believe)? yet I can see nothing wrong with the wiring or soldering in the SCART plug on these pins.

It might be that the 200uF capacitor wired to the appropriate pin is faulty (I don't have any testing equipment). However this would mean all the faulty DC cables had identically faulty capacitors and all on the same pin - is that likely? Surely some might have been used on either the blue or green carrying pins both of which seem to be fitted with the same type.

Obviously these cables are faulty and need to be returned if you're unlucky enough to buy one. What I'm personally interested in just trying to understand exactly what the problem is and whether it's DIY repairable. Hopefully somebody who knows something about SCART plugs and cabling might be able to explain it from the description I've given.
 

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