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Thread: Verdict: Mini ISN"T grounded Real time help!!

  1. #1
    Newbie Red_Beard's Avatar
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    Verdict: Mini ISN"T grounded Real time help!!

    Ok, I have my whole car torn apart right now, so I'm hoping some one can reply with some useful advice soon because I have to piece it back together and go to work soon.

    I've been having a hum over my stereo for a while, as posted before

    I just stripped a usb cable, and attached the usb cable's ground to the chassis ground, it went away, a little bit. (the usb ground is pretty small)

    Is there anyway to ground the computer better than it is? The P1900 is grounded the best (in my opinion) it can be.


  2. #2
    CarFrontEnd Creator iamgnat's Avatar
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    There are always ways, but none that I would advise.

    I know it's a royal PITA, but except for the very fortunate few that got lucky we have all been there. As in real estate ground loops are all about location, location, location.

    As a few of us told you in your other thread, it is a matter of finding the right ground point and it is rarely an easy task. Sometimes the places that seem like the best (grounding at the same point as your amps) are the worst, and other times the worst seeming places work the best.

    No matter where you ground, you need to make sure of 2 things.

    1) You are grounding to bare metal (scrape paint away).
    2) The ground line is short (no more than 6" is a good rule of thumb).

    Have you fixed you power wiring yet as discussed in the other thread? Given your inexperience with this kind of stuff (again, we've all been there) I highly advise you invest in getting someone else (a real car audio shop NOT some big box store). Go to a few and try to discuss what are doing and what you want out of the system. If they don't want to talk beyond giving you a work estimate or trying to upsell more work/equipment, move on to one that will spend time helping you better understand the benefits and limitations of what you are asking for. Those shops are out there and the knowledge you gain from them is well worth the money you spend on their labor.

    At the same time they fix your power line, they should also be able to work on your ground loop issue too.

    -dave
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    CarFrontEnd (now it's own sub-forum!!!!)

  3. #3
    Newbie Red_Beard's Avatar
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    I looked up my car, and found ground points, scraped away paint and grounded EVERYTHING there.

    What it really seems like is that the PSU isn't grounded enough. Right now I have the mini hooked up to a inverter, and it has WAY less hum. Barely anything. Just something else I'll explain later. Anyway, with the inverter setup, its grounded good enough. With the CarNetix, it seems to be lacking that. Both devices too, the screen and the mini.
    Anyway to get that thing really grounded?

    A problem I've been finding is that when my audio gets to a certain dB level, static comes over. It sounds horrible. When jacked up all the way, you can't hear anything other than static. Is that just part of the ground problem (happens with the inverter) or something with the radio? (Radio is grounded to that holy spot)

  4. #4
    CarFrontEnd Creator iamgnat's Avatar
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    Quote Originally Posted by Red_Beard View Post
    I looked up my car, and found ground points, scraped away paint and grounded EVERYTHING there.
    There is nothing you can "lookup" to find a good grounding point. Every vehicle is different even if they are same model off the same line.

    What it really seems like is that the PSU isn't grounded enough. Right now I have the mini hooked up to a inverter, and it has WAY less hum. Barely anything. Just something else I'll explain later. Anyway, with the inverter setup, its grounded good enough. With the CarNetix, it seems to be lacking that. Both devices too, the screen and the mini.
    That is absolutely a ground loop issue. Your P1900 is grounded in the wrong place. There is nothing we can tell you about how to fix this issue besides to keep moving the ground point until the problem goes away.

    A problem I've been finding is that when my audio gets to a certain dB level, static comes over. It sounds horrible. When jacked up all the way, you can't hear anything other than static. Is that just part of the ground problem (happens with the inverter) or something with the radio? (Radio is grounded to that holy spot)
    Is this turning up the volume on the Mini or on your radio (didn't you say in your earlier thread that you are using the mini through an AUX input to your radio?). If it's turning up the volume on the Mini, you should be adjusting it there. Instead you should set it to a level (you'll have to play with it) and then use your radio's volume control.

    If you are adjusting the volume correctly, it could be a defective AUX device or another ground loop issue. I have seen aftermarket AUX units that were poorly made that did things like what you describe.

    -dave
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    CarFrontEnd (now it's own sub-forum!!!!)

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    Ok,I'm going to try to find a better ground for the P1900. As once I do that, I think most of these problems are going to go away. I think I'm going to power the screen via the fuse block I put underneath my center console.
    Speaking of which, I have a 12ga running to that block, I want to put a switch on it, you think that's possible? It has everything for the sound running off of it.

    No matter what I turn it up on, it hear static. If I turn the radio all the way up ,it does it. Or if I have the radio at "pretty high" and the mac busts out some loud music, you'll hear hints of it on the bass and high treble.
    The Aux plug is pretty small. Maybe i should have just gotten a more expensive HU. One with a built in AUX..

  6. #6
    CarFrontEnd Creator iamgnat's Avatar
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    Seriously, save yourself the time and frustration of fighting with this and take your car to a shop that can help you get it sorted out. I understand wanting to do it yourself, but based on the descriptions you have given you are still too new to this to be able to get good help from anyone without physical access to the car to see what has been done.

    I just don't want to see you turn your car into a colander

    -dave
    My pathetic worklog.
    CarFrontEnd (now it's own sub-forum!!!!)

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    Here's my plan. My ground is getting pretty crowded. I'm going to get a terminal bus and ground everything there and ground the terminal to the ground. Making sure everything is grounded correctly.

    Now, I have to run a bigger wire for my newly installed fusebox. Right now its only 12ga wire to that thing. Like you said earlier, risking a fire. So, I'm going to go to Advanced Auto Parts and get a super long 8 ga wire to it. Is there a way to put a switch on that? I don't want things pulling power the whole time, only when I want it to. Maybe a solenoid? Its coming directly from the battery, no fuse. If I were to put on a fuse, what fuse would I put on a line like that? I want all the amps I can get, right?

    Good news, for now. With the inverter setup, I put a GLI on it, and the audio is very very impressive. No static, only when the radio goes to 70-80. No matter what setup I've had so far, anything exactly 70 and above the static begun (only on aux), so somethings wrong there, but I live with it, its too loud anyhow.

    But, I really appreciate the help Dave, things are looking better, and more organized since you've helped me. You've shone plenty of DC powered light on my setup.

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    So, I'm going to go to Advanced Auto Parts and get a super long 8 ga wire to it. Is there a way to put a switch on that? I don't want things pulling power the whole time, only when I want it to. Maybe a solenoid?
    Wire the 8 guage + wire direct to the battery. Use a circuit breaker (60 amps should be sufficient) instead of a fuse as this also doubbles as a kill switch (presuming you're happy having your kill switch under the hood, as this is where the circuit breaker should be mounted - close to the battery)

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    well, I want to shut it off everytime the car turns off, so that's why I was thinking solenoid. I like my hand switch I had before, for the computer. But I could live with the power being controlled by the ign.

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