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Thread: Really weird laptop/dock issue, sound card disappeares from PCI bus

  1. #1
    Raw Wave shotgunefx's Avatar
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    Really weird laptop/dock issue, sound card disappeares from PCI bus

    Ok, so I go to set up the new laptop permanently in the car and run into the weirdest thing.

    First off, a little bit on my setup.
    Dell laptop with Advanced Port Replicator running off an inverter. Debian Linux is the OS. Screen is an 8" Lilliput touchscreen.

    I've tested this all in my house without issue, even running it off an inverter off a 12v battery.

    First problem I notice is a god-awful loud rythmic buzz, almost like a digital signal, on/off, on/off, about 300ms in duration each part, but there's some loud crackles over that, it seems to me to be noise from the laptop.

    Also, anytime I turn on or off the touchscreen a really loud pop coming from the speakers (the touchscreen/line-converter both run off the same 12v regulated supply)

    No here is where it gets weird, the line-converter is hooked up to the headphone jack on the dock. Now, I've done this with lot's of devices, MP3 players, etc without issue (today too). But for the life of me, there's no sound. Just that god awful noise.

    First I think it's some inverter problem. I dig a little deeper and discover the problem. According to lspci, there is no sound card. Basically, if I boot with the headphone jack plugged in, it does not discover it when booting as if it doesn't exist??? WTF?

    Also, X doesn't start right unless it's in recovery mode, no log, nothing, just hangs with a text cursor. It seems that while the input event for the touchscreen has never changed for me over hundreds of reboots, it's always different when the jack is plugged in and I boot normal.

    Now, even weirder, If I pull out the cable out of the headphone jack while the computer is running, the computer dies!, you see the battery icon for a fraction of a second and the laptop is shutoff instantly. Did this everytime I tried.

    I spend hours beating my head against this. I know the dock works, just had it plugged into my stereo.

    So after much frustration, I try the headphone jack on the side of the laptop itself.

    It works perfectly. Only a very slow rolling scanline line from the inverter (had this with my last setup too)

    I'm stumped. Anyone have any ideas as to what could possibly cause these strange symptoms?

    NOGAF, but my ears *****ING hurt

  2. #2
    Raw Wave shotgunefx's Avatar
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    So I reran all the grounds so that the amp/line-converter/inverter were all grounded to the same point.

    Still had a little hiss, but not nearly as bad, though now the touchscreen had [b]a lot[b/] of static.

    The headphone jack wasn't quite as bad either, still no sound making it to the speakers, but it wasn't installing killing it when unplugged.

    So I throw a hailmary and pick up a ground loop isolator from RatShack.

    Everythings golden (except using the built in dock headphone, maybe it was damaged the first go around?), even stranger, I was getting a problem previously that I had attributed to me screwing around with X. The sound card would be blocked on X loading and I had to reload alsa to get it to unblock. This only started happening during the install. Never happened in the house.

    This no longer happens. WTF?

    Oh well, problem solved, but I'm still confused.

  3. #3
    FLAC Jahntassa's Avatar
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    Well, for the stuff with the dock, i'd try the Dell forums. They might have more insight as to what's going on with that.

    Glad you got the other issues taken care of.

  4. #4
    Raw Wave shotgunefx's Avatar
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    Quote Originally Posted by Jahntassa
    Well, for the stuff with the dock, i'd try the Dell forums. They might have more insight as to what's going on with that.

    Glad you got the other issues taken care of.
    Didnt' see anything there, but they're not big on linux support. My first laptop I ditched because the headphone jack was physically broken, but the dock was fine. Problem was that the linux drivers didn't support the doc in the audio drivers

    Always something. I'm just really suprised grounding could cause such issues with the laptop itself. Then again, the Inspiron 8600s have had a host of issues anyway.

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