I've got a few strange symptoms on a machine I built:
I think I've got a ground loop, maybe at my cable modem.
I found an article on solving ground loops, but I'd love to confirm that these symptoms are all related to that issue, and make sure I'm not dealing with multiple loops.
I've got an ohmmeter around somewhere, but not a lot of experience using it.
(I assume I should be stripping the machine down, disconnecting and unplugging it, and adding components one at a time to test...)
Any general advice on hunting down the issue(s)? Anything I should be paying special attention to? If it is only the cable modem, what's the best way to solve it -- an isolator?
If you already suspect the modem, I'd suggest that rather than stripping the machine down and adding one component at a time, it may be easier to first remove the modem and see if that fixes it.
No concrete suggestions on what to measure tho.
I had a computer a couple years ago which wouldn't reboot if a flash drive (or anything USB with storage) was plugged in. That part turned out to be a BIOS setting, it was trying all 'removable drives' before the hard drive, and the hard drive turned out to be the boot device of last resort after a 10-minute time out (it was a freaky BIOS, let me tell you).
The sound card issue could be grounding, but a simple check would be the volts (not ohms) between the bare metal of the case and a known ground, like an outlet ground pin if you know that's good or a water pipe. Then you could check voltage between your PC and the cable connector as well. Running your ethernet cable through a UPS 'filter' should match that ground to the PC's as well.
The audio connection part: Are you running Vista/Windows 7? Windows post-Vista contains 'protection' routines that disable your analog audio outs when 'protected' (hi-def) content is played with a media player. Only digital (in this case your digital out and an internal Aux) outputs are supported so that you can't redirect audio data to a tape recorder (the 'analog hole'). More here.
So, at least I've given you the possibility that all three of your issues are completely unrelated. I certainly can't prove that they aren't related, but these are just the first three things that popped into my head.
Something (a head) once fell onto my computer and hit a USB drive plugged into the front. Now, whenever something is plugged into that port, the computer restarts. That USB port is broken beyond repaid
I just installed Ubuntu 9.04 and have been unable to get sound functioning. I have a set of USB speakers (not USB powered with a stereo plug... they are totally USB).
I've tried plugging them directly into the tower as well as into the USB port on my Dell 2405FPW monitor. Both USB ports are functioning correctly (I tested by sticking a flash drive in there - they both read it), and the speakers are functioning correctly in Windows.
If it's relevant, I have an SB Audigy 2 sound card that came with the computer, but is not being used.
EDIT: These are the speakers - Logitech S-150 USB Speakers
You may have to assign sound output to them with PulseAudio. There's a WIKI about configuring PulseAudio here, but it comes down to just a couple of steps:
1. Install pavucontrol, the PulseAudio volume control panel, and launch it. Switch to the playback tab.
2. Launch something that plays sound (like Totem). It should show the VU meter for the playback.
3. Right click on the VU meter and choose "Move Stream... >" You should be able to select your USB stuff if HAL detected it properly.