This feedback is driving me nuts!!!!

**recoil** · 04-17-2008, 04:58 PM

I've installed my computer it all works fine, when the engine is off.

Turn the engine on and I get a schreeching sound, that doesnt change with revs, but I have noticed if Im stopped for a long time at eg. lights, the noise goes moing the stearing wheel noise comes back, if I put full lock right or left the noise goes away.

Now the computer sound output is fine, ive tried computer speakers whilst the engine is on and no strange noises. I've bought a USB sound card I read somewhere that, that helped, but not in my case. I bought a Groun Loop Isolater, that just distroted the sound to a point I couldn't hear what song was playing, but the strange noise did go away.

I have the car stereo, computer power supply, mobo and CF card all grounded to the same place. The computer isnt in a case its mounted in the glove box hence the ground wire going to the brass riser for the mobo.

I think thats all you need to know lif you need more info ask and I will tell

Thanks

**Xargon321** · 04-17-2008, 08:50 PM

i would try a isolation transformer, that seems to help this issue.

**brucedog** · 04-19-2008, 12:48 AM

Hey Recoil,

I read your post and at first said "I don't want to touch this one- could be too messy."
But not replying or trying to be of assistance is the easy way out...

As a long-time electronic tech and electronic hobbyist, I have been taught that toubleshooting, isolating the problem is the heart to fixing things, and often the hardest part. It comes down to eliminating possibilities.

So, here we have a car electrical system, a carpc with dc/dc supply connected, and audio ouput of carpc connected to amplifier(s), right?

I had a little trouble reading/understanding your post, but I noticed that you said GLI actually made the problem worse. Sure sounds like you've got a ground loop, though.
I wonder if you have the ground correct on the mobo, or maybe you have grounded too many points on the mobo, and thus created a ground loop.

First, can you power your carpc with some other 12v source such as power supply or battery fro other vehicle. Then, when you run the carpc connected to your audio amp(s), you can see if the noize is still there.

Do you have carpc connected to more than one amplifier? Can you just connect it to one amp or switch between amps to try and isolate the noisemaker?

Hmmm, could the noise be induced noise do=ue to your mobo not being in a case?

I sure wish that I could see the unit. Seeing yields so many more clues. Any carpc fanatics in your town?

Parting shot: pull all wiring off, and reinstall one by one, making sure they all go where they should. Also, I personally ran a 12v ground cable from batt to chasis, and grounded all amps, carpc stuff to that very same exact point, to hopefully eliminate circulating currents.

Best of luck and blessings.

**wazza** · 04-19-2008, 01:17 AM

This is a little tricky ?
The reason why you are not getting the noise interferance when using comp speakers are because they are magnetically sheilded no Electromagnetic external interferance
The interferance you are picking up is from a main Bus OEM loom back to the battery , hence all the electrical harmonic cross talk (powersteering pump electronic relays and so on ) could be the way you have signal routed your DC supply or audio signal send

I would try moving the PC motherboard /case away from the glove box housing first temp to see if you are picking up harmonic interferance from a body control module circuit then if this does not work i would do the same as stated in previouse thread and seperate the power source to the battery directly and see if this corrects the issue i would all so re route my audio signal cables from my Pc to the Amp another direction you may be picking up a ground loop from a OEM loom , try another installation method
try another amp input isolate or narrow down if it is a sinal issue or a power rail issue in the power supply circuit first.
Good luck hope all works out /