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I have a headset for my desktop computer. It's an analog device with two 3.5mm jacks, one for the headset, one for the microphone. It also has inline volume and microphone toggling.

By wire was chewed up by a cat and torn between the headphone jacks and the inline controls.

I have repaired the headset by re-soldering the wires. It works fine...sometimes.

When I plug the headset into one phone, and the microphone into another, I can play audio onto the headset and record my voice just fine on the other phone, with no crossover.

However, when I plug the cables back in to my computer, the headset works just fine, but there is nothing but what sounds like some background interference coming from the microphone when I test it. I have tried it with two sets of audio jacks on the system, both produce the same result.

Why would it work on the two phones, but not on the computer? This isn't making much sense to me and I hope it would to someone else.

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I think it sounds like the mic signal and headset ground lines are shorted together. The mic signal will be shorted to ground when both plugged into the same computer (i.e. shared ground)
When they don't share a ground, the problem goes away as the only common signal path is up to the short and should be of negligible resistance.
Testing with a multimeter would confirm this, just touch one probe to the tip of mic jack and other to headset sleeve (The other larger contact - I'm assuming mono TS Jacks, as opposed to TRS jacks)

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  • \$\begingroup\$ They are both TRS jacks. It's a bit late for me right now, but I'll definately test this some time tomorrow. This seems like a good answer 'cause it's something I never would have thought of. \$\endgroup\$ – Jonah H. Sep 26 '11 at 8:30
  • \$\begingroup\$ Okay - if TRS test both tip and ring on the mic jack (keep other probe on the headset sleeve) \$\endgroup\$ – Oli Glaser Sep 26 '11 at 8:47
  • \$\begingroup\$ Testing with the multimeter shows there is not an absence of resistance; there is high resistance between the mic tip/ring and the headphone sleeve. \$\endgroup\$ – Jonah H. Sep 27 '11 at 1:59
  • \$\begingroup\$ Also, as far as I can tell, there is only one ground. There's four wires, three with shielding (red, green, blue), of which I know red is the right headphone channel, and one without shielding, which must be the ground. \$\endgroup\$ – Jonah H. Sep 27 '11 at 2:16
  • \$\begingroup\$ Sounds like they have a shared ground then, which is indeed more common for these things. What was the resistance reading exactly? Can you test the readings between every contact and edit your answer with the values? \$\endgroup\$ – Oli Glaser Sep 27 '11 at 4:00
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This is more query than answer although an answer may be found in answering. Will edit or delete in due course.

Did it DEFINITELY work OK on the SAME PC you are trying it on now prior to the chewing?

Did you definitely match colours etc when resoldering.

Have you shorted two wires together? This can be checked with a multimeter on ohms range

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  • \$\begingroup\$ Yes, it worked Ok on the same computer. Yes, the colors were 100% matched up No, I do not think that anything is shorting out. Because I can plug both jacks (headphones and mic) into two separate phones at the same time, and there is nothing wrong with the playback or recording, I assume nothing is shorting out, unless there is some reason why plugging them in to the same device would cause a problem. I've tested it on two computers and it has the same problem. If I plug the headset into the computer and the mic into the phone, it works fine too. \$\endgroup\$ – Jonah H. Sep 26 '11 at 2:52
  • \$\begingroup\$ Additionally, if I switch the jacks on the computer (headset=>mic jack, mic=>headset jack), I can record just fine by speaking into the headset. I am not able to hear anything coming out of the microphone, not even a little bit. \$\endgroup\$ – Jonah H. Sep 26 '11 at 2:54
  • \$\begingroup\$ Russell, like you suggest yourself this is not a proper answer. I'm not going to downvote it, but I would think this would do better as a comment. \$\endgroup\$ – stevenvh Sep 26 '11 at 6:08
  • \$\begingroup\$ @Stevenh - The aim was to try to give him some logical questions to think on. He no doubt has been doing this but its easy to miss the obvious.Comment style is not amenable to setting out point by point suggestions. \$\endgroup\$ – Russell McMahon Sep 26 '11 at 11:55
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The mic and headphone ports on your computer might not have a common ground thus your mic might not have a complete circuit if the soldered joint isn't good.

You might be able to easily test this by leaving the headset plug unplugged but run a small wire from it's ground to the mics ground.

The reason it might work on your phone is a shared ground or it could even be that you're using a 2 x three pole 3.5mm to 1 x four pole y-split adapter which would join the mic and headset ground connections.

EDIT

Sorry, just read your comments on Russell McMahon's answer. So this probably doesn't help.

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