Should any ground complete a secret in a VGA?

[Locke141]

I'm making a VGA to SCART cable. I noticed no matter what ground I test on one end the circuit is closed with any other ground at the other end. IE if I test the Red ground (or any other ground) pin on one end and the Green return (or any other ground)  at the other end the circuit is closed. Shouldn't the Red return be isolated from all the others?

Is my cable damaged?

[yotsuya]

Do you mean circuit?

[Locke141]

Do you mean circuit?

Yep. 

Dyslexia + iPhone = What the heck does this guy mean.

First post fixed.

[qrz]

ground is common for all RGB drives.

if u test the ground points for continuity , there should be no more than a couple of ohms at most between any two ground points .
( "cold" side of power supply - isolation from mains)

note:
500uA max allowed AC leakage from hot /cold side of smps

[Locke141]

ground is common for all RGB drives.

if u test the ground points for continuity , there should be no more than a couple of ohms at most between any two ground points .
( "cold" side of power supply - isolation from mains)

note:
500uA max allowed AC leakage from hot /cold side of smps

Thanks but I'm talking about a VGA cable. I got and tested a different higher quality VGA cable and on this one the 5 ground pins are indeed isolated from each other. I'm going to have to start over with this one.

[MonMotha]

High quality analog video cables use mini-coaxial cables internally for the video signals.  These will have a separate shield acting as ground return for the analog video.  This is why various video connector standards, including HD15 VGA, have dedicated ground pins for each video line.  They're almost universally just connected together at each end, though.  The only ground that's sometimes treated differently is the DDC/Auxiliary Power ground which you're probably not even using, here.  Even it will probably be connected in some way to the video grounds, but it may be treated separately in layout to try to minimize noise pickup.

[Locke141]

High quality analog video cables use mini-coaxial cables internally for the video signals.  These will have a separate shield acting as ground return for the analog video.  This is why various video connector standards, including HD15 VGA, have dedicated ground pins for each video line.  They're almost universally just connected together at each end, though.  The only ground that's sometimes treated differently is the DDC/Auxiliary Power ground which you're probably not even using, here.  Even it will probably be connected in some way to the video grounds, but it may be treated separately in layout to try to minimize noise pickup.

Thanks MonMotha,

Thats good to know. Then it sounds the VGA to SCART cable I made should work fine. The second VGA to tested I've actually got from friends that run a post house so I'm not surprised that each ground was isolated in that one.

I'll keep the one I already made as is. I also make a simple VGA female to SCART mail box.