Raspberry Pi Forums

Hi i tried a RCA 3.5 audio with video cable on the raspberry pi 2 using a old tv. I got a scrambled picture with sound.
Does anyone know what the cause is?

expandables wrote:Hi i tried a RCA 3.5 audio with video cable on the raspberry pi 2 using a old tv. I got a scrambled picture with sound.
Does anyone know what the cause is?

Do you know the pinout of your cable? Does it match the specified pinout for the Pi?

http://www.raspberrypi-spy.co.uk/2014/0 ... ideo-jack/

Have you configured the video output to match your tv?

http://elinux.org/RPiconfig#Video

A scrambled picture means you have signal and GND reversed.
The sleeve is signal, ring#2 is GND. Your plug has sleeve as GND and ring#2 as signal.

So if i have signal and GND reversed what do i do?

expandables wrote:So if i have signal and GND reversed what do i do?

Rewire the plug or buy a new Apple or Zune cable that's compatible.

DougieLawson wrote:

expandables wrote:So if i have signal and GND reversed what do i do?

Rewire the plug or buy a new Apple or Zune cable that's compatible.

OK so cut the yellow off and put in on the red?

expandables wrote:

DougieLawson wrote:

expandables wrote:So if i have signal and GND reversed what do i do?

Rewire the plug or buy a new Apple or Zune cable that's compatible.

OK so cut the yellow off and put in on the red?

No. The GND pin is common to all the signals. You have to rewire the 3.5mm plug.

OK so how can i rewire the 3.5mm cable? I am saying should i cut off the yellow cable and put it where the red is and cut of the red and put it where the yellow is?

expandables wrote:OK so how can i rewire the 3.5mm cable? I am saying should i cut off the yellow cable and put it where the red is and cut of the red and put it where the yellow is?

No.

You cut off the 3.5mm plug and throw it away. Then you buy a new 3.5mm plug with solder terminals and you solder the three signal wires (red, white and yellow) to the correct 3 pins. Then you solder all three signal shield wires together to the remaining pin.

Basically, if your signal and ground are reversed you are SOL and should buy a new cable. But, before you do that, use a multimeter to double-check the pin order.

Might as well buy a new cable. Or can i stick the 3.5mm cable in and leave gnd out? For example not putting it straight in.

expandables wrote:Might as well buy a new cable. Or can i stick the 3.5mm cable in and leave gnd out? For example not putting it straight in.

Maybe. What do you think?

Have you used a multimeter to check the pinout?

I have no multimeter and i know little to nothing about electronics. Dumb "dunkey" here I am just here learning.

I will buy a multimeter i also plan to take an electronics course. But i will experiment and cut off the 3.5mm and put a new one on.

expandables wrote:I will buy a multimeter i also plan to take an electronics course. But i will experiment and cut off the 3.5mm and put a new one on.

Whoa! How is your soldering experience? If you are just learning I recommend that you don't do this. It will be an exercise in frustration. The 4-pin 3.5mm plugs can be hard to find, and the solder pins inside it are tiny and tricky to connect.

You can make a simple continuity tester using a torch bulb and a battery. Even if it's taped together you could use it to test which pin of your cable is connected to where. (Do this with the RCA cable *not* plugged into the Pi).

One way to get a cable with reversed ground to work is to cut the video cable and reverse like this:
Usually the cable has the video wire in center and braided wire surrounding the center as ground wire.

Cut exiting Video wire:
3.5mm plug 3 --------------------//-------------------------RCA Center
3.5mm plug 4---------------------//-------------------------RCA Ground

Swap and connect like this:
3.5mm plug 3 -------------------0--------------------------RCA Ground
3.5mm plug 4 -------------------0--------------------------RCA Center

Thanks for the help appreciate it! I have never solder anything in my life so i will buy some more rca cables to test.

expandables wrote:Thanks for the help appreciate it! I have never solder anything in my life so i will buy some more rca cables to test.

Ok. It would not be your best introduction to the world of soldering.

Here's a couple of cheap continuity testers you can make.
http://blog.carlynorama.com/2014/04/03/ ... y-testers/

It would be a worthwhile exercise to build one and verify the pin configuration of your cable. Then you can be sure the cable is wrong. But if it's right, then you have a problem elsewhere. You can also verify that a new cable you buy has the correct pin configuration.