RCA Audio works with negative disconnected

Other Hardware Audio
1

Hoping someone can shed some light on this for me because Google isn't helping and curiosity is killing me.

I have an adapter in the back of my TV which allows me to connect an svideo cable and RCA audio plugs into a scart socket. At first I got audio and a black and white picture before discovering that disconnecting the audio jacks gave me a perfect picture.

More experimenting reveals that just connecting the inner part of the RCA audio jacks gives me perfect picture and perfect sound. If I push the RCA plugs right in the sound remains the same but the image goes black and white.

Can anyone explain how the audio works with only the positive part connected? It just doesn't make sense to me...I thought a circuit needed to be complete for electricity to flow...

Cheers,
LongTom

2

Hi LongTom,

you have probably a ground loop somewhere (highest probability is through the power supply). If you have an earthed power supply, it goes through the earth.

Now, it's not normal at all that you get something good with ground disconnected, while connecting everything as expected leads you to a bad picture (this would push in favor of a ground loop however)

I would recommend you to check with an ohm-meter the ground path between your system and the TV.

By the way... a stupid question: any relationship with Arduino °-)

Benoit

3

BenKissBox:
Hi LongTom,

you have probably a ground loop somewhere (highest probability is through the power supply). If you have an earthed power supply, it goes through the earth.

Now, it's not normal at all that you get something good with ground disconnected, while connecting everything as expected leads you to a bad picture (this would push in favor of a ground loop however)

I would recommend you to check with an ohm-meter the ground path between your system and the TV.

By the way... a stupid question: any relationship with Arduino °-)

Benoit

Thanks for that, I will try to investigate further tonight.

Only connection to Arduino is that my multimeter is in the same "bits box" and I couldn't think of a better place to turn to than here for some electronics advise.

4

That's a strange problem but you could make a short RCA extension cable with no ground/shield, or with the ground unconnected on one end. Then wrap the connector junction in electrical tape or heatshrink it for a semi-permanent assembly.

I have an adapter in the back of my TV

:smiley: Did you buy it on ebay? :smiley:

5

Capacitave coupling to ground can provide the extra connection that is missing.

f I push the RCA plugs right in the sound remains the same but the image goes black and white.

Sounds like there is something else supplying a ground.