Persistent hum on my connected phone
MichiganTelephone:
Jeff205, yours is an interesting situation because you say when you remove either line, the hum goes away. That sounds less like a power supply issue and more like a poorly designed phone to me, although I hate to blame the phone because it could be something else entirely.
The thought that popped into my head when I read your last message was "ground loop." You sometimes hear it in analog sound systems where you have two different sources on different inputs and if you plug both in you get hum out of the speakers, but not if you disconnect either one (and it's a big reason why optical cabling has become so popular). The thing is, though, that a two line phone should not be susceptible to that — even if you had two commercial phone lines, there's no guarantee they are taking the same path through the building, or even coming from the same central office! So if you only get the problem when both phone lines are connected, then yes, it could be a bad phone. Would reversing the polarity of one of the two lines help? Possibly, if the hum is additive, but then again it could make it worse.
Anyway, if you don't get the hum when the commercial line isn't connected, then it's most likely NOT a bad power supply on the OBi. But since I'm not an OBi engineer, nor an engineer of the company that made your phone or your cable provider for that matter, there's really not much more I can say about that.
Jeff205:
MichiganTelephone, I'm afraid you're right. It may be the phone. I actually have two models exactly the same and they both do it. I will try the polarity fix just to see if that works...will let you know.
Jeff205:
I posted this on another thread and it solved my issue, but I don't want to break anything.
I am in the US, replaced my power adapter and my hum went away. My only concern now is will it hurt to use a different adapter. It is Input: 120VAC 60Hz 11w Output: 12VDC 500mA. It just the first one I put my hands on (I have several to choose from), so I mainly want to make sure I do not break anything.
BoomerForum:
Hi,
I have the exact same issue with my new AT&T 2-line phone. Did you find an answer and/or does anyone know of a good 2-line phone that works with both a POTS line and an OBI VoIP line?
Mark
Jeff205:
Mark,
I went to Radio Shack and picked up a power adapter that matched the original specs and everything works well now. No issues at all. I'm sure I could have bought a cheaper one online, but it was the quickest fix. On my latest Obi device, it looks like there is a filter to prevent this issue.
Good luck.
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