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laptop power supply question

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  • laptop power supply question

    ok im using one of those DC to AC convertors so my cars 12 volt is going to 230v and on that is my laptop charger which converts it back to 20v 6ampere... ok so first i took a 150watts convertor which made my laptop charger buzz all over the place which then offcourse hit my audio as well then i went for a 300watts convertor which is doing exactly the same... Why is my laptop charger making this buzzing sound when connector to an convertor it works fine in my home.. actually i dont care so much my charger is buzzing but this sounds is going through my audio as well. I tried installing an audio noise filter between the cables which kinda eliminated the noise but its still there aaaarrr

    somebody have any suggestions on how to connect this laptop right and what I exactly need???
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  • #2
    get a laptop cigarette lighter plug thing, and hardwire to the power.
    Teach me.


    • #3
      DC Auto Power Adapter for Notebook Computers here you can find DC Auto Power Adapter for Notebook Computers


      • #4
        I tried one of these also but this one putted allot of distortion on my screen anyways i had no problem with noise on the audio this time... So anything i can do to take away the noise from the screen?? could it be this car adapter wasnt simply powerfull enough for my lappie?? I took one from Belkin 120watts
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        • #5
          ground every connection

          try to ground your dc connections it may help


          • #6

            im not sure what u mean with ground the dc connection... If u mean connecting the minus cable to somewhere metal. I already did otherwise the convertor doesn't even work?? or i got it all wrong here???
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            • #7
              Here's the deal. Most inverters don't put out smooth clean AC current. Most of them just simulate AC and poorly at that. This is most likely the reason for all of your problems. You need to convert the 12V DC from your car to 20V DC directly. you should be able to find an adapter in walmart or online that will do this. Most of them plug into your cigarette lighter one one end and directly to your laptop on the other. Most have selectable voltages, anywhere from 18 - 22V should be fine. If your still getting noisein your audio or screen, use a line noise filter. You can get one from most auto parts stores. They are made for stereos but will function nicely with your laptop.
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              • #8
                Originally posted by S11D336B
                Here's the deal. Most inverters don't put out smooth clean AC current. Most of them just simulate AC and poorly at that.
                Many put out a modified square wave. By definition, square waves generate harmonics. Harmonics are the electromagnetic equivalent of a shotgun! If there is a receiver nearby, it will get hit!

                Noise filters, inductors and capacitors serve to smooth the edges of the waves and thus eliminate much of the noise. Sadly, some switching power supplies can do the same if not sufficiently filtered.

                Watch out, I have a soldering iron and a ham radio license (it's worse, it's an extra class license too!) and am not afraid to use them!


                • #9

                  I think i seem to be getting what is the problem here...

                  When I use the special car adapter i bought for my laptop the audio is fine only the screen has noise.

                  on my laptop normal power supply it states 20v 6a which means 120 watts
                  the car adapter I bought is exactly 120 watts. So probally what is happening here is that my laptop surges the maximum power of this adapter which is probally just enough to get it going but too weak to provide a good signal on my video out.. because when i use a short video cable its fine only when i use a longer one it start to get a noisy screen. So probally the video out signal is too weak to reach all the way to my lcd screen... The cable itself is fine as when I use the 12v to 230v convertor the video is fine only the horrible noise kicks in on my audio probally caused by the modified sine wave (i checked the convertor its not pure sine wave ) So I probally should go for an car adapter which could go up to 150 watts so I have some spare watts left then probally its solved i will look one up these days ill let u guys know how its going...
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