Neon Sign

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
I was asked by a restaurant owner to check the circuit to his neon sign. I have never worked on a neon sign and told him that. But apparently he had a sign company come out and they told him the sign didn't have enough "power". That is the term he used.

I took a quick look at the sign on my way out (we were eating there when he asked). It looks like only part of the sign is out. I don't know if the entire sign is fed from a single circuit or if it has more than one. If it's just one, I don't see how a under voltage problem would cause just part of the sign to be out.

He told me that the sign company said there was a chest freezer on the same circuit as the sign and that was what was causing the sign to not light. Seemed simple enough to just unplug the freezer to see if that made a difference but don't know if they did or not.

Anyway, I guess my question is do I just check voltage at the panel and then at the sign to see if there is any significant voltage drop?
And, would low voltage on the primary side of the sign transformer cause only part of the sign to not work?

Also, would there be more than one transformer for a neon sign?

I'm hoping a junction box that I saw at the base of the pole is where the supply enters as I don't intend on going up to the transformer. I just want to verify voltage and let the sign company deal with anything else.
 

GoldDigger

Moderator
Staff member
A typical neon sign has all of the tube segments in series, fed by what is essentially a constant current transformer.
The neon tube shows a negative resistance when the SRC strikes, and so requires a current limiter.
Unlike a fluorescent tube, this function is performed by the "transformer" which also supplies a high voltage rather than by a "ballast".
If the sign consists of several tubes in series rather than one long tube, then any that do not light are either shorted out or are carrying the current in a way that does not produce UV light to excite the phosphors lining the tube.

Tapatalk!
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
A typical neon sign has all of the tube segments in series, fed by what is essentially a constant current transformer.
The neon tube shows a negative resistance when the SRC strikes, and so requires a current limiter.
Unlike a fluorescent tube, this function is performed by the "transformer" which also supplies a high voltage rather than by a "ballast".
If the sign consists of several tubes in series rather than one long tube, then any that do not light are either shorted out or are carrying the current in a way that does not produce UV light to excite the phosphors lining the tube.

Tapatalk!
I couldn't tell from the short time I looked, to see if there were separate sections to the sign. But the section that is out is outlining an image at the top. That is probably one continuous tube and none of it is lit.
 
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