NOzone.

What’s wrong with an electronic transformer in a neon clock?    This question, or some variant of it, comes up often anytime neon signs and specifically neon clocks are being discussed.

Some will tell you it is fine and makes no difference, others absolutely forbid the suggestion of using a modern type electronic transformer in this application.  One manufacturer I know of will deny any warranty claim if a customer fits an electronic transformer to their clocks.  I lean more toward the latter group, but with a possible exception.  It really depends upon the specifics of the installation.

Ozone.  O3.  A triatomic molecule of Oxygen.  It is naturally created in the upper atmosphere by ultraviolet light disassociating a molecule of regular oxygen (O2)….this results in a separate pair of free oxygen atoms which then promptly attach themselves to an O2 molecule and form the O3 ozone molecule.  Ozone blocks much of the harsh UV light from space and is therefore needed in the upper atmosphere to protect life on earth.  Hence all the fuss about ozone holes and hairspray back in the 70’s and 80’s.  But here on the surface, ozone–while useful in certain filtering applications, can create havoc and health problems.  The right stuff…..in the wrong place.

You can readily recognize the smell of ozone even in minute concentrations.  After a good thunderstorm.  Standing by  a waterfall.  Or sniffing around behind an old fashioned TV set with the high voltage CRT.  Thunderstorms and waterfalls are associated with clean smelling air.  Part of this is due to the bit of ozone produced in each situation.  Falling water, by way of the change in entropy, can do minute amounts of ozone formation.  Thunderstorms, however, produce copious amounts.  The strong electrical discharge of lightning readily disassociates some oxygen molecules and just as in the upper atmosphere the atoms promptly bond with other O2 molecules to produce ozone.  Ozone is one of the strongest oxidants known.  It very rapidly attacks other materials.  In a filtering application it can easily bond to bits of other chemicals.  Hence the clean smell after a storm.

This clean smelling sensation is what lead to a lot of quack medical devices intended to produce ozone in a home or doctor’s office.  A multitude of these devices were built and sold over the years.  They almost always operate via corona discharge between two plates or in some models between two neon tubes that are only connected at one end and therefore illuminate by having the air gap between them take the place of the other electrode and connecting wire.  From a neon viewpoint this is an intentionally created electrical fault and results in a very discernable buzzing sound, flickering of the tubes….. and lots of ozone.

While there is merit to electrostatic air filtering and use of ozone for some cleaning functions, these things never really provided the claimed health benefits and if one were to be overexposed it would actually be hazardous.

So what of the clocks?   Well, to quote an old friend, “Here’s the deal…”  Remember I mentioned ozone is a great oxidizer?   Well.  It is.  Big time.  It will readily corrode many metals.  (gold, platinum, and palladium being notable exceptions)   If ozone were to be generated inside of a clock case, the geared clock movement would almost instantly fall victim to the corrosive effects.  As would the metal case, trim pieces, wiring, etc.  In addition to the direct oxidation by O3, there is another problem–Nitric Acid.  Air is mostly Oxygen and Nitrogen….and there is always some amount of humidity (water vapor–H2O) present.  Oxygen.  Nitrogen.  Hydrogen.  All readily available and happy if left alone.  Until that electrical discharge.  Then the free Oxygen atoms grab onto some O2 molecules to make some ozone.  Some of that will go to work oxidizing metal parts.  The rest will grab on and oxidize some Nitrogen, forming an NO3 radical…..this will inevitably get together with some of the Hydrogen from the water vapor and presto!–Nitric Acid.  HNO3.  Nitric acid is nice and strong and will then proceed to eat away at whatever it can get at.   (Btw, IF you needed nitric acid at home for a project, and I know some of you do– I won’t say why…. But I know.  😉 You could build a system to purposely generate it by simply feeding a stream of air across an electric arc and then bubbling the gas through water.)

So here’s where the choice of transformer comes in…

A conventional magnetic transformer with its coils wound onto an iron core transforms the voltage but the output frequency remains the same.  The voltage stepped up or down is a ratio of the number of turns of wire in the primary vs the secondary.  Feed in power at 60Hz from your wall outlet and the output will still be 60Hz at whatever the stepped up (or down) voltage is.

An electronic transformer, however, is more akin to a radio transmitter or switch mode power supply.  Some of the early models derived from the flyback HV circuits used in those CRT power supplies of early TV sets.  They not only raise the voltage, but they do so by running an oscillator circuit and this changes the frequency as well.  The result is a small, low cost, and lightweight device.  But the output frequency may be hundreds or even thousands of times that of the input frequency.  It is not unusual to have 20KHz output frequencies.  This is into the RF spectrum.

The issue is related to the so-called “skin effect”  DC power flows through the inside of a conductor.  AC flows closer to the outside surface, and at higher frequencies some of it readily leaves the conductor altogether as a radio signal.  Hence the ability to key a microphone and be heard on a radio thousands of miles away.  It also partly explains how Nikola Tesla was able to perform demonstrations wherein he had thousands of volts flow across him at currents high enough to illuminate lamps and not be electrocuted.

In a normal neon sign installation, all the connections are good…the tubes on proper stand-offs from the can, and all wiring spaced and insulated.  Thus in spite of the higher frequencies used with electronic transformers, the current goes where it should–lighting the tubes and not creating ozone.  But in a retrofit or a clock the story is often different.

Most vintage neon clocks, and those made to look old, have tubes mounted right up against the metal case, high voltage wiring is often laid from transformer to tube with it running along the metal case, etc.  The cases are often enclosed, possibly even weather resistant.  This scenario is tolerable up to a point with the traditional 60Hz magnetic transformers.  Granted, they CAN and do sometimes generate some ozone, but it is less likely unless a wiring fault is present.  Swap one out for an electronic transformer and all other things being equal, the propensity to create ozone inside that case will be increased.    The reason goes back to the tendency of the higher frequency power to want to escape the intended conductive path.  Tubes and wires close to the metal shell create an almost ideal condition for some of that energy to leak and as it traverses the tiny gap between tube or wire and case it will knock a few oxygen molecules apart (just like in the ozone generators mentioned above) and they will in turn bond with others to create ozone, or combine with the nitrogen and available water vapor to make nitric acid–both of which are very bad news to your clock.

So, for the most part….use a traditional coil and core magnetic transformer in your clock restoration.  It is not only more authentic but also less likely to cause this problem.

But.

What if you or the customer wants the electronic type?   They do offer some nice features–in addition to being inexpensive, lightweight, and low power consumption, they often are equipped with safety shutdown features, etc.   Can you use one in a clock?    A small modern cheap plastic one, sure, very likely…..on a rare vintage and valuable one made of metal?….Well.  Maybe.

IF the installation of the transformer, wiring, and tubes can be done in a manner to give ample spacing to minimize ozone generation….and IF the case can be vented to help get rid of any that is created…..then MAYBE you can do it without problems.  I have not gone this route myself but I do know some people who have had very good results with these mitigation efforts and using a small Tech22 transformer.  (Tech22, formerly called Tech2000, makes really good little electronic neon transformers that are ideal for sculptures and other small hard to fit applications….I’ve used them since 1990 in all sorts of things without difficulty…….If I were to try an electronic transformer in a clock, this would be my personal preference to try.)  Again, it will come down to the specifics of the installation….you might be able to fit and route things well enough in one style of case but not in another.

In spite of the possibility of making it work, I still lean towards sticking with the coil and core magnetic transformers in vintage clocks.  Why risk damaging a valuable or irreplaceable antique just to save a couple of bucks on a transformer?