sundance-communications.com/forum Forums Wiring - Telecom Carriers - Trunks & Services Security, Alarms and Paging Speaker Noise

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.

You said two power supplies and the noise is only on the ceiling speakers.

Do the bull horns use one power supply and the ceiling speakers the other? If yes then check the power supply and power cables. My guess is the power is intermittently shorting to ground or some thing that it shouldn't.

Now, one power supply powers the bull horns and the other supplies the ceiling speakers. As I mentioned in my first post. Power supplies have been replaced and all new cat 5 cables have been pulled to the speakers.

Is the noise a low hum? You said it sounds like something shorting out, so do you mean clicking? These things usually pick up AC induction, which would be a hum. If that's what it is turn off the breakers one at a time until it goes away. That will at least let you know what circuit is causing it. Also if it is AC induction shielded speaker cable grounded on one end should fix it, you're gaining nothing using CAT5. You could try grounding all the unused pairs in your CAT5, one end only and make them common to ground.

Its not a hum like a ground loop hum. Its is more like crackling, like the sound you hear when welding. Speaking with Valcom the OEM, they state shielding the speaker run is not necessary. We all know that the OEM does not always no best, so it might be worth a try to shield the cable. This system has been up and running since 2001. Just last year 2011, no building change, this noise starts. I would like nothing better then to start throwing breakers. My issue is the breakers I need to throw, control our computer systems and offices. The second issue with throwing breakers, this noise is so erratic that we can hear the noise only once a day. Maybe the next day 4 times, maybe 30 times in one day. This noise follows no suit so I cant relay it back to any type of AC that would start and stop like that.

Wouldn't hurt to ground your unused pair to see if it would help.

Unless the horns and ceiling speakers are different audio feeds the problem has to be in the power. Try plugging the power into a different AC circuit. A good way to test if noise is being picked up by audio pair is when the noise is happening short the audio pair together and see if it stops.

I did disconnect tip and ring on all the speakers. Noise is still here, so it is on the power side. I did pull a isolated 120 volt circuit to the phone system and replaced power supplies. I'm thinking the issue lays between the punch down block and the speakers. But what????????????????????????? No motors, wires are high and tight. No nicks.

Think I am going to try what Bill suggested and ground all the unused pairs of the cat 5.

Remember that since all the drop ceiling speakers are (apparently) in a separate zone from the horns, you are running two of the 3 zones. ANYTHING that gets on the speech pair from any speaker is going to ALL the speakers, but not to the horns. Also, it would seem that you still have 1 unused zone in the
2003. Move the speakers to it and see what happens.

We are using all 3 zones. The controller was replaced already so I think its safe to say not a controller issue. Zone 1 Bull horns, Zone 2 upstairs offices, Zone 3 lower offices.