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Old 24th September 2004, 03:51 AM   #1
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Default need help with carputer install, buzz/hum

hi all,

this is my first post here and i'm hoping you can help. my current setup is a Lilliput touchscreen (plugged into the cig lighter), compaq presario 1688 laptop running XP (running off the laptop battery for now), and my factory radio - a Becker CDR-220. the car is a porsche boxster.

when the car is running, i get alot of noise. don't know if this is 'alternator noise' because i'm not too familiar with it. i just know that it is unlistenable the way it is. when the car is off, it sounds great.

i have played around trying to find the source of the noise and i believe it is coming from the touchscreen. when i unplug the screen the noise goes away. the screen came with a cig lighter adapter that has a big "egg" in the middle of it, and i have heard these eggs are noisy.

i am planning on hardwiring all of this eventually, but for now my issue is the unbearable noise. do you think it needs to be grounded somehow, and if so, HOW would i ground it? i am a complete car audio novice, so you'll have to spell it out for me.

thanks in advance!
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Old 25th September 2004, 04:28 PM   #2
Volenti is offline Volenti  Australia
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How are you feeding the pc audio into the car's system?

To isolate the touch screen as the source of the noise, use the ac adaptor, if the nose goes away (or turns into a 60hz hum) then bingo.
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Old 25th September 2004, 04:40 PM   #3
djQUAN is offline djQUAN  Philippines
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since the PC runs on its own battery, the touch screen and the car stereo are the only ones running off the same electrical system. so you got ground loop. and probably you're listening to alternator whine?

you could use a ground loop isolator. it will be connected between the car stareo and laptop computer.
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Old 25th September 2004, 07:47 PM   #4
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thanks guys!

to answer Volenti's question, the factory radio has an AUX input, so i go out of the laptop (1/8" stereo plug) to stereo RCA into the radio. i eventually plan to hardwire the laptop power, so will i have the same issue when i hardwire the laptop?

can you recommend a ground loop isolator? i will go search the web to learn about them, but wondering if you have experience with them...

thanks!
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Old 26th September 2004, 02:13 AM   #5
djQUAN is offline djQUAN  Philippines
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if you're going to power the laptop with the car battery, you might get the ground loop again.

I don't think ground loop with the touch screen and laptop will be a prolem since both runs on digital signals. just wire them on the same power supply taps.


as for the ground loop isolator, you could easily get one from your local radio shack.
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Old 26th September 2004, 06:25 AM   #6
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just so i have this straight...

if the touchscreen is the problem, a ground loop isolator between the car stereo audio in and laptop audio out will take care of this?

is there any way to better ground the touchscreen?

thx!
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Old 27th September 2004, 05:04 AM   #7
djQUAN is offline djQUAN  Philippines
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the ground loop isolator would work if you're using the laptop battery for power. not sure though when it's already hardwired.
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