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Thread: Dc-Dc intelligent usb noise problem.

  1. #1
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    Dc-Dc intelligent usb noise problem.

    Hello, I'm having a weird issue with my power supply. When I hook the power supply up to constant hot I get a very unusual noise. I can't really explain it, it's a really high pitched and crackling sound. I've been doing car audio for a while so I'm used to troubleshooting ground loops and alternator whine. This isn't like that at all. I ran new power and ground direct to the battery and as long as the laptop is hooked to the supply I get that noise. I rerouted everything to the battery and powered it up and it's still the same issue. Absolutely perfect running off the laptop battery. I brought my second battery to the car and powered just the supply to the laptop and it still did the same thing.
    I'm at a loss. I've changed every single cable in the car.
    Anyone have an idea?
    Thanks

  2. #2
    FLAC SNOtwistR's Avatar
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    Is this powering your laptop/charging laptop battery? If it is I think your are running close to the max of the unit. I have heard a high pitch noise coming from one of mine, (i have 2 in my truck) it was caused from too much draw. Just a thought SNO

  3. #3
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    Yeah it's powering the laptop and charging the battery. I thought just powering that one device is what it as intended for? I have very short runs of power and ground it's a saturn so all the battery's and equipment are in the trunk.
    It's a Panasonic Toughbook so I would think the draw wouldn't be that high. I guess I'll mod my other laptop and try it.

  4. #4
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    Hi
    I think most of these issues with this psu is with the laptops earth...Im having a hell of a time getting the interference on the screen cleared up...whilst mucking around I pulled the input earth of the psu whilst still powered up (ooops ) and it caused the monitor to ape, it looked like the psu was earthing itself via the monitors earth??????
    Ive connected another earth to the psu metal case and its helped a bit..Im now thinking of trying earthing the laptops chassis to the car somehow, but not sure if that will help or cause more issues...
    Not much help soz just some observations from my Neanderthal tinkering...... maybe Ill use a wooden club to beat it into submission

  5. #5
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    I've even tried running it without the monitor just to see if it was a ground loop that way. Didn't change anything. I'm at a loss. I've grounded every accessible port on my laptop with no change at all. I've got my second laptop ready to go so I'll try it today and see how it goes.

  6. #6
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    Hi
    In your orig post you didn't say where the sound was coming from.....
    Im assuming the audio if so what sound card are you using? also have you tried something like this http://www.jaycar.com.au/productView.asp?ID=AA3084

  7. #7
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    Yeah.. I was getting noise even when the laptop was muted. I pulled every thing out of the trunk today and put it back in and now the noise is gone. No idea what it was. Now I have a different problem.. LOL
    When I plug the on/off switch line from the power supply into the laptop it turns off. Sigh...
    I was getting the noise on both the built in sound card and my usb external sound card.

  8. #8
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    Hi
    What turns off the laptop or the psu? you might just have a doggy psu... Im not using the on/off lead from the psu as I have a remote switch on the dash for that
    I remember reading someone else had issues ....think this is the thread http://www.mp3car.com/power-supplies...-usb-info.html

  9. #9
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    It shuts the laptop down. Measuring the psu leads that are supposed to connect to the laptop switch shows resistance like the switch is stuck or shorted. With just my lead plugged into the laptop it works fine. I'm going to take it all out of the car and set it up and see what it's doing.
    Thanks for the help.

  10. #10
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    Figured that out as well. My fault again. The socket I put in the laptop for the switch was shorting and causing the shut down. So.. audio noise gone and power supply working as expected. Now to find the source of those horizontal lines on my screen. lol
    I still have no idea where the noise was coming from. But it's gone so I'm not going to worry about it until it comes back.

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