Hello all,

I'm writing here because I have been faced with an inexplicable phenomenon regarding some switches with neon glow lamps on a couple power strips/surge protectors I own.

One is a 1996 Tripp-Lite Isobar; the other one is a cheap ~$12 one from Walgreens, purchased in 2018.  Both have rocker switches with neon indicators in them, which have been behaving in a bizzare way under certain "ambient" lighting conditions.

Basically, I've noticed the neon indicators only seem to work correctly in the switches when the lighting in the surrounding room is "just so."  On the cheap Walgreens one, the light initially worked for a few months, but due to cheap quality, it started to fail within ~2 months and began to flicker.  Then, one night, something odd came about.  The light was on (flickering) on the power strip when the overhead light was on, but when I turned off the overhead light to go to bed, the neon indicator went out completely, flickering/blinking in the dark only occasionally.

Now, I also have an old 1996 Isobar surge protector, with a neon indicator that seems to be "dead" under normal operation - it won't even flicker 99% of the time.  Or, is it?  Every time I've used it in the garage or family room (with not as good overhead lighting), the neon light would NEVER light up, PERIOD.  But then I brought it into the well-lit kitchen, plugged it in, and the light flickered on and sustained a neon discharge.  WTF??? It also worked in my bedroom with the overhead light on, but I can't get it working elsewhere.  Note there is not a wiring issue; I've tried it on both new and old wiring, and the results have been the same every time, with the ONLY varying factor being the amount of light in the surrounding room, whether it's natural or artificial light).



So, how on earth could ambient lighting (note artificial lghting is on a totally different circuit and not remotely related to the power strips' functionality), impact whether or not a neon indicator lights up?

I remember that Uxwbill talked about this in one of his older videos, dead neon indicators in power strips suddenly coming to life under flourescent lighting. I'll see if i can find it, might help to give some explanation.

There are some neon bulbs in switches installed back in the late 1970s in a few of my church buildings that long since burned out, but will come back to life kinda during certain atmospheric conditions like stormy weather.  Kinda neat seeing them flicker to life for a bit.  Same thing happens with some of the lights in the power surge protector switches where the neon bulbs went out previously. 

These neon lamps are lack of Tritium, which means that they requires light to start and sustains a discharge. A common phenomenon with modern fluorescent glow starters. The exact thing, happening to my Osram HQI-TS 70W/WDL Excellence double ended MH lamp, which is lack of Krypton-85: https://www.lighting-gallery.net/gallery/displayimage.php?pos=-125319

I don't think the Neon indicators ever contained any radioactive aid (due to cost reasons - handling that stuff makes the process VERY expensive these days).
The problem is, when they are new, they somehow ignite well on the 120V mains. But after they age, the dark ignition voltage increases, so the 160Vpeak is not enough to ignite them.
When illuminated, the photo emission from the photons hitting the cathode lowers the voltage below the 160V, so it works.
This phenomenon is known since Neons were ever introduced and it has been always one of the major life limiting factor. In many equipment designs the Neons were combined with incandescents near by (as panel or scale illumination source), most equipment design just assumes nobody present when in darkness, so the indicator not working there was not a problem.

In 230V areas we are lucky, as the 320V gives enough margin for them to work even in darkness, but at 120V it is normal they dont.


By the way this effect is the reason, why many modern Nixie clock designs use blue LED underneath the Nixie display tubes: It may appear as just a "hip" feature, but in fact it allows the tubes to operate reliably even after decades of storage (thse tubes are decades old NOS, but they were never designed for that long storage)

Wow!  Very informative.  Thank you so much for your explanations; I knew there had to be a logical reason somewhere.

I must say, I find it very interesting that visible light, in and of itself, could lower the gas's resistance, thereby causing the neon lamp to "function."  Pretty wild if you ask me.

Yep, really weird that this happens, but I've noticed it too.

Wow!  Very informative.  Thank you so much for your explanations; I knew there had to be a logical reason somewhere.

I must say, I find it very interesting that visible light, in and of itself, could lower the gas's resistance, thereby causing the neon lamp to "function."  Pretty wild if you ask me.

It is not lowering the resistance, but it is "priming" the discharge with free electrons. Really very few electrons (single to few dozens) are what it is all about. When present, they do not provide any measurable conductivity, but they start the ionization avalanche, building trillions of them (then we start to talk about some plasma conductivity) in an instant. If there is no electron, the avalanche may just not start. Because it is just the few electrons dictating how the arc starts, the ionization start is very random, dictated by governed by a poison distribution (darker light means fewer electrons, so more random so erratic discharge reignition).