kuo

i'm running a laptop setup and i'm almost completely done except for this noise issue. i am using a dc-dc cigarette adapter for laptops for power.

http://store.l-f-l.com/cgi-bin/cp-ap...=DC-DC-ADAPTER

the noise is only there when the laptop is plugged in. when it runs off it's own battery, i have zero problems. as soon as i plug it in, lots of bad things start to happen. the speakers make annoying buzzing/crackling sounds. buzzing is constant, crackling is random. this is with the engine off. when the engine is on the noise gets worse as rpm's go up. also the xenarc starts flickering so the noise is going through my audio and video when i plug the laptop in.

i've done some searching and someone had similar symptoms and ended up saying that his laptop's sound card was messed up, but it seems to me that if the sound is fine when the laptop is running off batteries, then it shouldn't be broken. please help. i have no idea what to try next.

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grepzen

Does the pitch (of the noise) rise and fall w/ engine RPM?

Most likely, a simple noise filter will do the trick for ya.

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kuo

it does go with the engine rpm's but there's also noise when the engine is off. is the noise filter still the answer?

kuo

ok so i went and got a noise filter from radioshack. so do i chop the connector off the cigarette light adapter for the laptop and wire this in between?

WhiteRabbit

I think he meant an RCA filter. try grabbing a scrap of 20 gauge wire and wrapping it around the shield of your phono to RCA converter plug, on the RCA side. ground it and see if the noise goes away.

I found a noise filter got rid of a vast majority of the sound, but not a perfect fix. grounding the rca shield finished the job. later I found it worked fully without the noise filter in place.

kuo

thanks whiterabbit. i'll give it a go.

ccblanket

kuo, I wonder if you ever got rid of that noise. I am having the exact same problem with my laptop setup. When it runs off its battery, it is fine. as soon as I plug in the dc-dc laptop adapter, it starts that nasty noise which is worse than the engine whine.

I'd appreciate if you could share your solution (in case you found one).

anode

Run all grounds, the ciggy lighter, the amp, etc to one single point. You are probably creating a ground loop with the grounds scattered through out the car.

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tbethune_87

Ive had that same problem, not running audio and everything, but wen i had my standard cd system playin, plug tha laptop in to the cigarette lighter, it would crackle and the backlight on the cd wen with the beats.....i put a 4wd battery in my car, now shes all good....

-Newbie

tbethune_87

LOL, I read tha dates on this thread....i think its dead!

ccblanket

not dead (yet) .

what is a 4wd battery?

sivart321

I have the same problem. I can say for a fact that noise filters and ground loop isolators on the RCA's will not always help in this case. I also get noise through the VGA cable, using high quality VGA coax cables with ferrites on both ends.

I have almost given up, attributing it to the simple nature of these cheap switching DC-DC power supplies.

One option, if the correct voltage is available for you, is to use the carnetix power supply to power the laptop.

I have stopped worrying because I have decided to go to a micro atx/opus solution. The laptop had so many other problems that it is not worth the hassle.


Goodluck!

pancit175

The cigarette lighter is always the noisiest place for power. try running a new ground for the cigarette plug or just run power straight from the battery.

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krasniak

i have the same dc-dc adapter and i've conected it (adapter & lcd TC) to new wires grounded in other place - nothieng happened; problem wosn't solwed what shoud I do GLI ?? or what) PS Nobody in my poor cantry don't wont to help me, they say that there can be toomany posibilitis and too many work to find the problem. But i know the dc - dc adapter makes all the mass.

jaripetteri

I have also the very same problem with the same power supply. Have you measured the "grounds" electric potential between power supplys input and output grounds?

I'm just wondering if the power supplys input and output grounds are not connected together that could explain why there is the ground loop on signal line. I'll check that tomorrow and hope I do not blow up my setup totally...

I also get that engine rpm relaited noise when the charger is not connected on laptop but its a bit lower. When unpluged the laptop ground is not connected on cars ground anyway so grounding could be the problem there also, right? I have extra regulators for 12V and 5V's and those are already grounded on cars ground.

At theory the shouldn't be any problem if I connect laptops charger ground on cars ground, right?!? I need to do some studing there anyway...

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