Grounding or power issue I can't figure out.

[TDot 10+ year member]

Here's my situation, it's away from audio, but the carputer section seems dead. I have no other indications or symptoms of grounding or power issues, I do not have big 3 and don't think that has anything to do with it.

I have a computer with a dual screen set up, the main touchscreen, and the factory nav screen. My regular touchscreen has no issues at all. My nav screen with the regular car info feeding it has no problems either. Now when I feed the computer to the nav screen I start to get slight interference like hum bars. When the base really hits, that's when I really see the problem.

Currently I have all my audio and car grounded and powered together. 4g running from battery to a D block and feeding the stuff. And then the ground from everything to another D block, and from that to a point where I see other stuff is grounded from the car...so I know the grounding point is good.

What I've tried:

1/ used a laptop in place of the carputer with its own power and everything is fine.

2/ used an extension and plugged the carputer power to my house and everything is fine.

3/ discoed the power to the audio set up, took a wire ran it outside of the car back to the negative battery, and also tried the engine block and I still see the problem.

4/ connected the carputer to the cigarette lighter and still see the same problem.

Can noise be introduced into the power wire? Can the battery cause this? The other option I'm considering is to ground the carputer to the same point as the nav screen. Will that make a difference? I don't really want to do that because it will be hell to pull up my dash and trace that harness and wire. And then I doubt to run a 12-14g ground wire trunk to front is really good...I'm not running a 0/2-4g wire just for a computer.

Any other suggestions?

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[PSturmer 10+ year member]

Everything should have the same ground. This way all of the components are at the same potential which reduces noise. If this doesn't work then it sounds like you need to isolate your power supply to the computer. Perhaps a DC isolator would work, but I don't know of these eliminate any AC component- which is the noise. Off the top of my head I know a complete isolation could be achieved by using a dc to ac converter, and then convert it back to dc with.a ac to dc converter.

 

[PSturmer 10+ year member]

And to answer youyr question, noise can be introduced via the positive or negative wires. This is unlikely to be from your youtr battery but rather from how everything is wired. I wouldn't ground anything to your chassis, instead running a full ground from your battery. Make sure all electrical components are grounded to the same location. You can also investigate into this phenomenon:

Decoupling capacitor - Wikipedia, the free encyclopedia

 

[PSturmer 10+ year member]

Instead of fixing the core problem you can also try covering it up. One thing would be grounding the outside jacket of the audio link. But if your current electrical system is in bad shape then thiks could cause more problem- ie if various gronds are at different potentials then current flows between them. Anther fix, one which is safer, is to put a ground loop isolator on the signal wire

 

[tommydh 10+ year member]

If its not too much trouble what model carputer aare you using? voltage requirements, connecting cables type needed/used. It sounds like theres an interference issue. but I cant pinpoint it without more info. You could diode isolate the DC to the ac inverter or look into one with an Isolated ground. In reg A/C apps in computer rooms there is actually 2 grounds 1 is equipment grounding just like normal other is diectly to xo of transformer. I will be able to help more with more info.

 

[TDot 10+ year member]

1/ The decoupling capacitor won't work for me...I don't believe...because all of the ones I see are circuits and chips, not "outboard gear".

2/ Is it wise to rearrange where the factory nav/computer/audio/communication is grounded? You say everything should be grounded to the battery, and everything should be grounded together; that would mean taking my system grounded in the back and running that to the battery, and then taking the factory stuff and reroute it to the battery.

3/ What do you mean by grounding the outside jacket? There is no audio component in this video feed.

4/ Putting a ground loop isolator on the video feed sounds good, and a good first step since the interference isn't that bad, however all the ones I see for video are BNC connectors and I need one for RCA...I'd prefer not to add adapters in the mix. Will the ones for audio work? Or do they work on different platform, freq, or something?

I'm using a zotac ad10 plus receiving power through a dc-dc USB regulator at 19v that's connected to the power fed from the battery. I cut the wallwart off the factory ac adapter that came with the computer, and soldered the leads to the regulator. There is no ac conversions.