LCD wiring? Help needed ASAP!

**DrSergioDJ** · 02-06-2004, 12:08 PM

Ok, i got a 5.6" into my hands, but my testing time is limited.

So, it has 4 wires (i only need the video stuff and not the audio)

1) yellow - video input
2) brown - video ground
3) black - power ground
4) red - +B 12V

Ok, so for 1,3 and 4 i know what they are, but what the hell is "Video ground"? The owner told me that it needs to be connected to a "-12V", but I don't know how to get a -12V in my computer?

Help needed as i can't get the owner on the phone!

Thank you!

p.s.

it's a no-name lcd (it's known in europe..) so i can't tell you the brand.

**honclfibr** · 02-06-2004, 12:36 PM

Sounds like you have one of those LCDs wired to accept a composite RCA input signal.

Yellow is the positive terminal of the RCA, which should be connected to the prong of the plug. Brown is the negative terminal of the RCA which should be connected to the circular surround.

**R3l0ad** · 02-06-2004, 12:50 PM

-12 is a simple ground like the (-) terminal on a battery, or a hardground to say the metal frame of your car.

**DrSergioDJ** · 02-06-2004, 12:59 PM

uhm..i know where to get -12v in my car...but i need to know where to get it in my pc...

**honclfibr** · 02-06-2004, 01:08 PM

-12V is NOT the negative terminal of your battery. -12V is 12 volts below the ground reference. You would have three wires, one would be +12V, one would be ground, and the third would be -12V. If you measured between +12V and -12V there would be a 24 volt potential difference.

It is possible to find +/-12V supplies however they are not common. But from the pinouts you listed, I don't believe your LCD requires -12V. Certainly, video ground would not be -12V, so something is strange here. It really sounds like you have a pretty basic LCD wired to accept NTSC or PAL input, that you connect the red and black wires to 12V/Ground to power the backlight and logic and the yellow and brown wires are the positive and negative inputs for the PAL/NTSC signal.

**R3l0ad** · 02-06-2004, 01:10 PM

Oh well one of the black wires on the molex connectors will work

**honclfibr** · 02-06-2004, 01:19 PM

Connecting the video signal ground to the power supply ground will work *only* if there is a common ground path between the LCD supply and the input device's power supply, i.e. if they are both running off of AC power and grounded to the wall outlet ground prong. If your input device is floating, i.e. a laptop running off of battery power, you need to tie your video ground to the input device's signal ground, otherwise your video signal has no ground reference and you will not get an image.

**DrSergioDJ** · 02-06-2004, 02:28 PM

ok, thanks for all of your answers, i managed to get a picture on it (it was a white&black only + really ****ty one, but i'd say cause i only "rolled" the wires together and I blame it all on the wires

)

I'll buy it, thank you guys!