Neon Sign

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BackInTheHabit

BackInTheHabit

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Lexington, Kentucky
Got a call from a restaurant today.

Their phone line near a neon sign is picking up a buzzing noise. Tried several choke filters on the phone line, noise still there. Noise lessens when switch to neon sign is turned off. Phone plug and switch are within 4' of each other.

I recommended changing the switch thinking that there is some arcing in the switch may be the cause. The switch is original and am thinking it's just worn out.

Anyone have any advice.

Is there a filter that can be put on the neon sign?

What are my options?
 
does the phone have a power supply plugged into the same circuit as the sign? is the sign properly grounded? what type of phone wire is being used? could you re-pull in shielded cable or run in a conduit?
 
things to thing about ? but it sound like a loose ground

things to thing about ? but it sound like a loose ground

Does the switch have more than two circuits in the box ?
Is it switches and a receptacle ?

Well, did you check the Telephone ground at its service point ?

Aside from that did you use a tone device on phone line to seek out a short or even ohm the lines
themselves or use a simple phone line tester ?

Did you check for proper electrical installation at the neon sign?

I want to ask is the phone on a base and is in fact a mobile phone that is wireless?
If this is the case they make a 900Mhz mobile phone that don't pick up the lower levels of interferences.

Is the mobile charger on the same circuit as the neon sign ?

edit: deleted a duplicate line
 
Neon signs use high frequency/voltage capacitor circuits that are bit bit more powerful than flouresant systems and not as well shielded.

If practical try to place a piece of sheet metal between the two and see if the buzzing diminishes. Cat 5 twisted will not help you but twisted and shielded will if installed correctly. Only ground one side of the shield, if you ground both ends it will not help.

If the phone system goes into some sort of PBX, change the impedance matching setting.

Also be aware that neon signs create a plasma field that is looking for things to ionize that are close to it, try giving it another ground from the case of the the sign power supply. The previous suggestion to put it on another circuit is a good idea too, but note that any power wires running near the sign will pick up the signal like a radio antenna. Hence, if you are an electrical hobbyist you may consider putting a low pass filter on the phones electrical supply.

If it is a cordless phone system, you are screwed.
 
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I agree that cat5 is better at resisting noise than cat3 or similar phone wire, but in a case like being directly next to a neon sign giving interference, If I detemined that it was the phone cable being the issue, I would go ahead and run shielded, but thats just me....
 
ultramegabob said:
does the phone have a power supply plugged into the same circuit as the sign? is the sign properly grounded? what type of phone wire is being used? could you re-pull in shielded cable or run in a conduit?
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No power supply to the phone. Neon circuit is on same circuit as other lighting.

Will be back on thursday morning and will see what type of receptacle it is.

Not sure of the phone wire type, it is inaccessible.

Pulling new home runs not an option. This restaurant has been here for many years, 20 plus, they are just reently having a problem.

I'm not convinced it is the neon sign since when the switch to the sign is turned off the buzzing is still there. There is a computer phone line on the same duplex phone jack, or phone line. I am leaning on the computer as part of the problem.

Changing phones doesn't help it still buzzes on different phones.

It is not a cordless phone either.
 
just for kicks, take some cat5 and run it on the floor all the way from the phone location to the interface and see what happens, that would rule out the existing phone line problem, then do the same thing by running an extention cord from the sign to a differnt circuit in the building, its worth a shot....
 
ultramegabob said:
just for kicks, take some cat5 and run it on the floor all the way from the phone location to the interface and see what happens, that would rule out the existing phone line problem, then do the same thing by running an extention cord from the sign to a differnt circuit in the building, its worth a shot....
Click to expand...


Yeah, and turning the circuit off that originally fed the neon light. Thought the signs power supply was the problem for sure until I read the buzzing remained after the sign was off. I have heard of this before when a phone line was ran next to an AC drive, but it was closer than 4' !
 
I've run into several phone problems involve a DSL line and Wireless network.

Seems the wireless network tends to "argue" with itself over the DSL line even with the filter installed. Many small businesses use wireless and put it near the phone board and phone lines (typically where the line enters the building).

I had two situations like this, both required me to move phone wires and reposition the wireless network. It also seems that the wireless b is worse than wireless g but both cause problems. This is regardless of whether they use cordless phones.

If you have a similar DSL and wireless network setup, consider moving them away from the phone wires (punch down panel or building phone line entry area), and keep them away from each other.
 
Back at the restaurant this morning.

Replaced single pole switch with a commercial grade single pole. Old switch was a residential switch by the way. Replacing switch helped.

Changed phone cord from wall jack to phone. Noise went away mostly. Recommended getting a filtered or shielded phone cord.
 
I am still not convinced if there is still noise on the line w/o the sign on, and can you honestly say replacing the SP switch really helped? There was less audio interference afterwards?
 
76nemo said:
I am still not convinced if there is still noise on the line w/o the sign on, and can you honestly say replacing the SP switch really helped? There was less audio interference afterwards?
Click to expand...

I can honestly say it helped because I was there.

It did not fix the problem it only helped.

And there was less audio interference after the fact. You can reach the switch standing by the phone that had the trouble.

Guess you had to be there.
 
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