I have been off and on trouble shooting this noise that comes over our PA speakers. Its a AC noise, sounds like something is shorting out. Only wish it has, then I would be able to fix it. This noise is erratic, it happens at different times and for different intervals. So I have been reading some of these forums and noticed I am not the only person with this problem. Ill list things that I have done.
Valcom 2003A PA System, ( 12 ) 24 volt drop ceiling speakers, 10 Bull horn speakers and 2 separate power supplies. We also have a radio receiver playing call on hold music. This music is also played in our production area through the bull horns. We have disconnected the receiver but still have the noise. Our phone system is located in our server room. All computers seem to be running good. You would think if a computer component is shorting bad things would be happening.
This noise never happens over the Bull horn speakers.
1. Disconnected speakers one at a time. Ran though all the runs and noise never stopped. All speakers have separate run to the 66 block.
2. Physically checked all cables running to the 66 block. No nicks ( from mice or snags ) no runs are running parallel with high voltage. No runs are laying over any light fixtures. All runs are cat 5. Ungrounded per Valcom. The longest run is maybe 60 foot. There are no motors or such in our drop ceiling.
3. Disconnect tip and ring from PBX
4. Replaced all power supplies
5. Replaced Valcom 2003A controller
6. Disconnected tip and ring from all speakers
7. Pulled a isolated 120 volt grounded circuit for the entire phone and paging system.
8. Bypassed the UPS
9. Replaced 66 punch down blocks for both speakers and for Valcom 2033A.
10. Pulled new cat 5 wire for all speakers
11. Replaced surge protector
12. Disconnect bull horns from PA system
13. Disconnect drop ceiling speakers from PA system. No more noise. But noise never happens over bull horns anyways.
Valcom says there is no way of testing each speaker. As I said before I have disconnect each speaker 1 by 1 and the noise is still there.
Now here is something interesting. We have about 50 digital Panasonic telephones in our plant. Only one phone will pick up this noise. This phone is located in our break room. If I disconnect the phone run at the 66 block, I still here the noise, even over the disconnect phone. We have 2 vending machines, noise existed before these vending machines arrived. We have a refrigerator but there is no correspondence between compressor starting and when we hear the noise. I have traced this run back to the 66 block. Again nothing wrong with the cable and no motors or cable laying on light fixtures. I could really use some more things the look at here. Ive done every thing that I can think of except find the problem. Oh, our telephone provider was absolutely no help. Valcom states Ive checked all that they know to check.
