atcomsystems.ca/forum Forums TDM Business Telephone Systems Panasonic Telephones & Systems "whine" on D1232

Hello All

First let me admit that I am not a Panasonic dealer, but was asked to “take a look at” a 1232 today.

The customer is complaining of a “whine” on the lines. It is on all phones. I disconnected the modular plugs that the COs are on going into the KSU, pressed a line key and the noise was still there. I expect that this rules out noise on the lines. To add some weirdness to the mix, an outside caller cannot hear the whine at all.
Station to station intercom calls are clear, no noise. I expect that this can rule out phone sets and interference on the station cable.
Just for kicks I power cycled the KSU-no change.

Has anyone ever experienced these symptoms, and did I miss anything as it looks to me that the only remaining point of failure is the KSU itself.


All help is appreciated…

high loop current?new provider possibly ?
do you have a spare 12x and cards that you can swap out to rule out the system problem? do you have dimmers on site on that lights?
I have had to ship off a tda 50 -1 for that problem

It would seem that you've tried everything. I would say you've eliminated all but the cabinet itself. Clutching at straws: anything in the phone room, computer server, UPS, etc? If you have no MOH, try putting in a MOH feed of some sort temporarily. I'd bet that what you are hearing is the 'switcher' P/S getting ready to die. It's high operating Freq is not being completely rectified and filtered.

the problem began soon after they switched from at&t to comcast. but the noise is still there when all the lines are removed from the system.

I dont think high loop current is a factor if the line is not on the system. am I not understaning your advice?

I agree High loop current is not the problem unless it has permanently damaged the same component in every C.O. port. (Possible) Do you have any unused C.O. ports you can test with?

I WOULD check loop current. High (over 28 ma) has caused damage for me. Not on a Panasonic system, however.

I have a customer with the same whine on a 1232. All my tests show it is only coming from the system. The caller from the home hears the whine, but the called person does not hear it. How did this finally get resolved?

If you can, roll out the cards. But I think Lightninghorse is right. I had a similar thing a few years back and it was the Power supply. High freq. hum in the background but it was also on sta-sta calls.

It is the power supply. I had two of them do the same thing within the past few months. The good thing about Panasonic stuff is that you can replace components. Lots of screws, but it can be done.