Persistent hum on my connected phone
MichaelW:
I just bought Obis 110 and 220, and now they are both giving a hum on a connected wired phone (haven't checked on a wireless one).
The person I call hears the hum very loudly, plus serious voice distortion and clipped words. Calls are not usable.
The 220 worked OK at first. I disconnected it and connected the 110 and the hum appeared. Now both units have it.
I can stop the hum, and stop the distortion my caller hears, but touching the metal rim around the Ethernet port on either adaptor.
Anybody have any ideas on this, please?
Shale:
Pay attention to the *** suggestion above. 1: Do you hear hum then?
Connect your wired phone directly to the OBi. Do not have any house wiring connected for this test. 2: Is the hum there, or was this the way you were connected all along?
3: Are you using the same power supply in each test where you hear hum?
MichaelW:
Thanks, Shale.
I hear the hum pressing ***, even when the local wiring is disconnected and the wired phone is direct connected to the Obi. Hum can be removed by touching metal part of Ethernet socket.
I hear the hum with two power supplies on the 110: the one that came with it (which has a small black cylinder inline with the cable, near its termination at the Obi), and the one that came with the Obi 202 (slightly bigger, no black cylinder inline). Both give hum. I have also tried plugging these power supplies in 'upside down' ie. reverse polarity in the wall socket.
Edit: also hums using a RadioShack 3-12v 1000mA adapter set at 12v +ve tip (model number 273-1680). Again, touching metal Ethernet surround fixes it.
MichaelW:
Like others before me, I have found that a wireless (Panasonic) phone connected to the Obi does not exhibit hum, or distortion for the person called. Seems like this will have to be my solution.
Shale:
Quote from: MichaelW on April 24, 2013, 12:33:34 pm
Like others before me, I have found that a wireless (Panasonic) phone connected to the Obi does not exhibit hum, or distortion for the person called. Seems like this will have to be my solution.
Make sure the power supply on your 2-line phone is grounded if it has a ground pin. If it does not, try turning that power supply around in its socket. Since the problem does not occur for the wireless phone I presume the problem would not happen if you used a phone that does not use external power either.
If you dial ***, hear the hum, and pull the ethernet cable temporarily, does the hum happen? I am not sure what that would mean, but it could point toward a solution. The only other think I can think of is to use a shielded ethernet cable if your are not doing so, and to use an unshielded cable if you are now using a shielded one.
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