Page 1 of 2 12 LastLast
Results 1 to 10 of 14

Thread: Help : Monitor interference problem

  1. #1
    Variable Bitrate
    Join Date
    Oct 2006
    Posts
    274

    Help : Monitor interference problem

    Ok well the problem is I'm getting really bad interference in my monitor. Scan lines coming across, darkened display, and it will turn completely off when the bass hits hard.

    I took my laptop out to my car and set it in the trunk right next to the carpc and hooked it up to the same VGA cable as the touchscreen and it worked fine, no interference, even with music blasting. This tells me that it's not the routing of the VGA cable that's the problem.

    So then I take the whole CarPC inside and test it on a real ATX power supply, no interference there either, which tells me it's not a problem with the motherboard.

    Where do I go next from here? Keep in mind there are a few other strange symptoms : One of them is that I get really really bad alternator whine (high pitched noise in speakers varying with engine RPM), but it only lasts until the computer's sound card turns on, the minute the sound card is active it goes 100% completely away. The other thing is that sometimes the computer will randomly reboot, I believe this is caused by severe voltage drops due to my very much lacking electrical system attempting to power about 2500W of electronics and sound equipment.

    Do I have reason to suspect the power supply? (OPUS 150W DC-DC) or should I blame it on my wiring? How and what should I test next?

  2. #2
    Variable Bitrate
    Join Date
    Aug 2006
    Posts
    257
    Sounds like a ground problem, I had similar issues with my laptop in the car.
    Checkout the Car audio section of the forum, there is a sticky in there that explains ground loop problems and how to trouble shoot them.

  3. #3
    Variable Bitrate
    Join Date
    Oct 2006
    Posts
    274
    Yeah it definitely sounds like a ground loop, however I don't understand why if it was a ground loop the audible noise would go away once the sound card powers up and the monitor noise would go away with a new PC, same power cables, same signal cables...

    I'm starting to believe that the problem lies in my power supply. In both cases where I was able to get the noise to go away, the only thing that was bypassed was the power supply. With the laptop I bypassed the whole pc and used the same wiring which eliminates the wiring as the source of the noise, and when I tested it in the house the only thing I eliminated was the power supply, which eliminates the PC its self as the source of the noise.

    Today I'm going to take a really long extension cord outside and hook up my regular ATX power supply that I used for bench testing the PC inside and try that in the car with everything else running (including the OPUS PSU) and if I still have noise I will unplug things, starting with the DC PSU.

  4. #4
    Variable Bitrate
    Join Date
    Oct 2006
    Posts
    274
    Update : I took an extension cord outside and hooked up a regular AC ATX power supply to the computer...

    The audible noise was actually far worse, but once again when the sound card activated, it went away completely. The monitor distortion was also completely gone.

    Any ideas?

  5. #5
    FLAC DodgeCummins's Avatar
    Join Date
    Oct 2000
    Location
    DFW area
    Posts
    1,386
    Did you ever think that maybe the voltage is dropping to your monitor when you have your stereo cranked?

    You could try powering off your computer power supply instead of direct...but since your computer is losing power also...

    Maybe you need to figure out a way to keep the voltage up...bigger alternator, second battery, a cap for your subwoofer amp etc.

  6. #6
    Fusion Brain Creator 2k1Toaster's Avatar
    Join Date
    Mar 2006
    Location
    Colorado, but Canadian!
    Posts
    10,045
    When you had your laptop hooked up to the screen, was the carpc running too? If there is nothing being drawn on the power cables going to your computer, then no interference will be caused.

    I think it is a cable interference problem.
    Fusion Brain Version 6 Released!
    1.9in x 2.9in -- 47mm x 73mm
    30 Digital Outputs -- Directly drive a relay
    15 Analogue Inputs -- Read sensors like temperature, light, distance, acceleration, and more
    Buy now in the MP3Car.com Store

  7. #7
    Low Bitrate
    Join Date
    Mar 2007
    Location
    Barbados
    Posts
    69
    Power your carputer from the same points as your amp. Connect the positive terminal of your PC to the positive of the amp and the negative terminal of the PC to the negative terminal of the amp. Getting a bigger alternator does not alway solve power problems. BTW Is there any distortion in your bass when it's playing. if there is you should check the wiring which connects the sub amp to the battery. Also check you headlamp for dimming (with and without the engine running) and get back to me.

  8. #8
    Variable Bitrate
    Join Date
    Oct 2006
    Posts
    274
    Here is basically how the wires are setup.

    I have two 4ga wires running from the battery to a buss bar located underneath the rear seat. That buss car has one 4ga wire going to the 1200W mono amp, one 8ga wire going to the 400W 4-channel amp, and one 14ga wire going to the computer's power supply.

    There is a second buss bar, which is exactly like the power one, except backwards. 3 wires run from the grounds of the amps (same gauge wiring) to the buss car, and then there are two 4ga wires going from the buss bar about a foot and half to a ground point. The ground point is directly in the center of the car, on the floor, it was completely sanded down and drilled (not a factory bolt or anything)

    One remote wire (16ga I think) runs from the ignition column and then splits to trip the relays in both amps and the PSU.

    The buss bars all had plenty of surface area to, they are all clean sanded down aluminum which metered at zero resistance.

    Here's some pics...











    As you can see, I did the best job I could keeping all of the power wires tied up together, and shoved as far away from the outside of the trunk as I could get them, while all the signal cables (which for the time being aren't neatly tied up) are running along the outside of the trunk and never crossing their path.

    I do not believe it is a wiring issue because when I used the laptop there was no monitor noise despite me using all the existing wiring (all amps were powered up as normal)

  9. #9
    FLAC DodgeCummins's Avatar
    Join Date
    Oct 2000
    Location
    DFW area
    Posts
    1,386
    Are those pictures of your positive power wire busses? Make sure you keep plenty of marshmallows on hand.

    Ok well the problem is I'm getting really bad interference in my monitor. Scan lines coming across, darkened display, and it will turn completely off when the bass hits hard...

    ...took my laptop out to my car and...

    ...test it on a real ATX power supply, no interference there either...

    ...The other thing is that sometimes the computer will randomly reboot, I believe this is caused by severe voltage drops due to my very much lacking electrical system attempting to power...

    ...Update : I took an extension cord outside and hooked up a regular AC ATX power supply to the computer...

    It looks to me that you have proven the problem over and over. You don't have enough power.

    If you have an external video card installed...then try your system without it. On mine, I could power a Geforce4 card...but not an ATI all in wonder...with the 120w Opus.

    Hook a voltmeter up and watch the voltage when everything drops out.

    Also have you wired your Opus up EXACTLY the way the instructions say? (all the yellow wires to +12v, all the black to GND) Do you have a heavy cable from the opus to your +12v?

  10. #10
    Variable Bitrate
    Join Date
    Oct 2006
    Posts
    274
    First of all I'm know what I'm doing, so I don't think the marshmallow comments are entirely necessary. One buss bar is for positive and one for grounds. In case you didn't notice both bars are bolted to a piece of wood which raises them off of the chassis and the positive wire has about 4 layers of sound deadener underneath it just in case somehow it gets bent in enough that the bottom of one of the bolts could touch the chassis.

    Also I'm sure the voltage issues aren't helping however I don't believe they are the entire cause of the problem. I'm well aware that my audio system draws more amperage than my alternator can dish out which causes the load to jump to my battery, however I never draw full power (play music really loudly) for long enough to significantly drain my battery. I've tested the battery engine off and it reads 12.X volts so it maintains a charge just fine. The other thing is that the OPUS power supplies are made specifically to withstand voltage drops, the manual says they can operate steadily between 8-19 volts. I've never gotten anywhere near there even with the amps drawing from the battery on bass hits. Also the final thing is that the interference is always there, not just when the amps are on or when music is playing. It does get worse when the amps draw lots of power, but it's bad enough to the point of the PC not being usable even with music off. I have not yet tried running the computer with the amps completely disconnected yet though...I'll give that a shot tomorrow.

    Oh and yes my PSU is wired correctly, this system has been functioning flawlessly for over a year now with the only modifications being the audio system and wiring. The interference problem just showed up in the last few weeks and without changing a thing went from annoying to crippling.

Page 1 of 2 12 LastLast

Similar Threads

  1. Lilliput TouchKit problem solved!
    By AAVfReaK in forum LCD/Display
    Replies: 4
    Last Post: 11-07-2010, 08:29 AM
  2. reconnected puter and now audio problem..
    By NYCdesignkid in forum Car Audio
    Replies: 2
    Last Post: 05-30-2006, 11:09 PM
  3. gps navilock and com problem
    By lele67 in forum GPS
    Replies: 0
    Last Post: 04-01-2006, 07:41 PM
  4. Problem with directshow filter and WMP
    By EricE in forum Software & Software Development
    Replies: 0
    Last Post: 03-01-2006, 10:38 AM
  5. Car Idle - power/amp problem?
    By TheFaze in forum Car Audio
    Replies: 1
    Last Post: 12-15-2005, 11:10 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •