Neon Sign Repair Questions

Hello all...
A number of neon signs were recently delivered to me in nonworking
condition. All but one are driven by an Evertron 2610 power supply.
Surprisingly enough, this power supply and sign combination were made
in the US. Nearly all of these signs did continuous duty, shut off
only by power outages.
The Evertron 2610 power supply is a pretty simple affair. It bases
upon an IRF2153 driver IC and two IRF730 MOSFETs. The output from
these is fed into a transformer that looks not unlike a TV flyback. As
found, most of the signs would start and then shut down. Through some
very interesting circumstances, I came to know that the power supplies
would operate normally if powered from a generator. Protection
functionality appears to be centered entirely in the IRF2153, though
there is also a line fuse.
Every capacitor in the power supply was bad. None were visibly bloated
or distressed...either the ESR had skyrocketed or the cap simply
registered as open. Most were made by Meritek, a company I had never
heard of before. With new caps, the first sign starts up and runs once
again.
However, I'm wondering if the neon tube is worn out. The sign consists
of three formed letters, each of which are supposed to be the same
color, and one has a notably different (lighter) hue than the rest.
Also noted are strange hissing noises from the tube (not the power
supply), the ends of the tubing near the terminal points becoming very
hot (sometimes to the point of making something start smoking) and
"pulsing" from inside the tubing. Every now and then, the misbehavior
will stop and things will be fine for a few seconds, just like a
failing fluorescent tube.
Throughout all of this, the power supply remains cool and seemingly
stable. It is rated for 5.5kV and 27mA current output, though I have
nothing with which to safely test this.
I'm wondering if the neon tube has simply become weak or damaged at
this point. All parts of the sign were made by divisions of Everbrite
Electronics, and it sure seems "convenient" if they would all fail at
roughly the same time.
How do neon tubes act when they fail?
William
Reply to
William R. Walsh
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"Neon" tube signs may actually be neon - in which case you can see through the tube and can see the neon plasma in the center of the tube and the color is the red-orange neon color. For any other color the tube in all probability has argon to start and mercury to run and produce UV to excite phosphors inside the tube. These are cold cathode fluorescent tubes.
The different color letter may mean the tube (or tube section) has been replaced with a near but different phosphor combination.
"Hissing" - arcing at the connection? - would also produce heat Corona discharge? Are the tubes clean?
If the tubes light my guess is problems are in the power supply, or external wires and connections.
Neon sign power sources, like other discharge lightning ballasts, are essentially constant current. When shorted they will produce only about 30mA (some are a standard higher current). When the sign is running the voltage might be 80% of the rated voltage.
If you have multiple signs can you wire between signs to substitute power supplies and tube sets to determine what works and what does not?
You might try sci.engr.lightning. It is not real active but has some very sharp people.
-- bud--
Reply to
bud--
Hi!
Each sign is made up of two tubes. The topmost tube is definitely a neon tube. There is a tube on the bottom that glows white, but I think it's a coating on the inside of the tube that makes the white color, like a regular fluorescent bulb.
The letter in question is part of a larger tubing structure. I can't think it's been replaced...the sign has barely ever been dusted!
The more I look at it, I think it's got to be arcing. The power supply itself is silent, at least as close I've dared get to it while the sign is in operation, lest it blow up. From what I can tell, again being nervous about getting too close, the noise is coming from the tube near the connection points.
The sign is a lot less filthy than it was. It's still pretty dusty in some areas that are hard to reach. I don't want to get too rambunctious with cleaning it.
The connections look pretty shifty to me. They are simply wires wrapped around the leads coming out of each tube and covered in a rubber boot. I'd have really expected something better. The wires coming from the power supply look OK, while the ones coming from the tube are black in color. I'm having a hard time deciding if they were made that way, or if they have somehow oxidized.
The tubes start right away and do light but are rather unstable.
I don't yet have the other signs on premises. The two I have now are different. When I get more of them, I plan to try swapping parts to see what works and what does not.
William
Reply to
William R. Walsh
Probably a common connection method - it is only 30mA. Black sounds odd - you could try scraping. Leads from the tube may be pretty fragile. You could run it without the insulator boot and look for arcing.
-- bud--
Reply to
bud--

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