1 Exam Prep Neon Techniques Tabs and Highlights

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1 1 Exam Prep Neon Techniques Tabs and Highlights These 1 Exam Prep tabs are based on Neon Techniques: Handbook of Neon Sign and Cold Cathode Lighting, 4th Edition. Each tabs sheet has five rows of tabs. Start with the first tab at the first row at the top of the page then proceed down that row placing the tabs at the locations listed below. Place each tab in your book setting it down one notch until you get to the bottom of a page. Then start back at the top again. 1 Exam Prep Tab Page# Highlight/Reason Contents ix Table of Contents Intro - 2 Luminous-tube Industry 3 A pure neon tube radiates five times as much red light for a given amount of power as does incandescent light. A fluorescent-coated tubes delivers almost three times the light of an incandescent lamp of the same wattage. How The Luminous 6 How The Luminous Tube Works. It consists of an evacuated Tube Works tube, fitted at each end with a metal terminal called an electrode. Inside the tube is a small amount of highly purified inert gas. Connected to the two electrodes is a source of high-voltage electrical power. 7 What Happens Inside the Tube. The gas inside the tube consists of millions upon millions of particle called molecules. When this happens, a current can flow through the gas, and this current produces the desired light. 7 Thus to produce a gas discharge electrons must be removed from neutral molecules and recombined with positive ions to form other neutral molecules. The practical way of producing this ionization is by passing a current through the gas. 7 Figure 2-1: Action of electrons and positive ions in gas-filled tube. 7-8 How the Current Produces a Glow. When voltage is applied to the electrodes, one electrode becomes positively charged, as shown in Figure 2-1 Shortly after voltage is applied to the tube, the whole body of gas is in motion. Electrons are liberated from molecules, free electrons combine with positive ions, giving off light as they do so, and then are blasted apart again. 1 Exam Prep Neon Techniques and Handling 1

2 8 The voltage supplied by the luminous-tube power supply is alternating; that is, it reverses itself so many times every second. In the U.S., current reverses itself 60 times per second and as a result, the glow is distributed evenly over the whole tube. 8 The Reason for High Voltage. Unless high voltage is used, the electrons will not be attracted strongly enough to start the ionization process In cold-cathode ballast systems, the secondary voltage is standardized at 750 and 900 volts. 9 Once the glow discharge has begun, however less voltage is required to keep it operating. 9 A special type of transformer, made especially for luminous tubes and called by a high-leakage reactance transformer, performs this voltage reduction automatically. 9 Operating Current. The required operating current depends upon the diameter of the tubing, the kind of electrodes used, the kind of gas and its pressure. 9 The current of neon signs and cold-cathode tubing is measured in milliamperes (a milliampere is one-thousandth of an ampere) which is the standard electrical unit of current. Operating currents in standard signs run from 15 to 60 milliamperes. In cold-cathode lighting operating currents may run up to 120 milliamperes. 9 The Effect of Gas Pressure. Usually, however, pressures in luminous tubes are expressed in terms of height of the column of mercury which that pressure will support. 9 The gas in the luminous tube, for example, is usually between 3 and 20 mm. The larger the diameter of tubing used the lower the pressure required 10 Figure 2.3: Curve showing increase of current as pressure is reduced 10 The Effect of Diameter of the Tubing. Glass tubes for signlighting purposes are usually made with glass varying between 7 and 15 millimeters in outside diameter. 11 Figure 2-4: The voltage per foot required to operate tubing of various diameters filled with neon gas. 1 Exam Prep Neon Techniques and Handling 2

3 11 The Gases Used for Luminous Tubes. The rare gases - neon, argon, helium, xenon, and krypton - are ideally suited for use in signs. 11 The Use of Mercury. The most efficient and only practical way of producing many colors requires mercury vapor and a carrier gas. 11 To start a current flowing from mercury vapor is not so easy as easy as with a gas, and for this reason a gas (usually argon or argon-neon mixture) is mixed with the vapor to aid the current flow. 12 Chemical effects inside the tube. If any impurities such as dirt, grease, or impure gas, are left in the tube after it is sealed off, these impurities under the action of heat and electrical stress, become chemically active. As they combine with one another, they may blacken the glass they may liberate the gas inside the tube. 12 Bombarding, an Essential Operation in Tube Making. The best way of getting rid of [impurities] is to heat the tube while it is being pumped out. 12 The simplest way of heating the tube and electrodes is by passing a current through the tube while it is still on the pump, when the air pressure has been reduced sufficiently to allow a heavy current to flow. 13 Electrodes and Tube Life. Sputtering. Sputtering occurs when the electrode, under the action of the heat to which it is subjected and the electrical forces which act upon it, flies to pieces bit by bit. The metal of the electrode gradually flies off and coats itself on the inside of the glass tube. Sputtering is accompanied by a decrease of gas pressure in the tube. This loss of pressure eventually males the tube inoperative. 14 Mechanical Requirements of the Tubing. To make a good joint between glass and wire, the glass must wet the wire, that is, adhere to it firmly. Molten glass and wire do not readily cling to each other in this way unless the wire is copper or copper coated. 15 Electrical Protection. The wires which lead from the transformer to the electrode leads are thoroughly coated with a high-resistance The entire high-voltage circuit is thus completely enclosed with insulation from start to finish. (Entire paragraph) 1 Exam Prep Neon Techniques and Handling 3

4 15 The Operations Involved in Making a Luminous Tube. (Note entire section) 16 Figure 2-5: A schematic layout of a box-type neon sign Constructing a Luminous Tube Sign. (Note entire section) Materials Used in 18 The Atmosphere. argon, helium, neon, krypton, and xenon Construction Tubes are called rare or inert gases. They are chemically inert. This means, that these gases are almost always found free, This fact makes rare gases ideally suited for use in luminous tubes. 18 Table 3.1: Gases found in the Atmosphere 20 Neon Gas. It is colorless and odorless, slightly heavier than oxygen and five times as heavy as helium. 21 we may wonder why it has attained universal popularity. The answers are its color, which at once caught public fancy, and its high efficiency, which makes it one of the best sources of light for advertising. 21 Table 3.2 Light Output of Luminous Tubes The Light Efficiency of Neon Gas. a standard 10 watt Mazda lamp gives 100 lumens of light, or approximately 10 lumens per watt. To get the same illumination value from a neon tube tubing would be required. 23 A neon tube will provide 10 lumens per watt in the red range Hence, for the red ray the neon sign is five times as efficient as the Mazda lamp. 22 Table 3.3 Legibility Chart 23 Helium. In the luminous tube industry, helium was used to produce a yellow or whitish light The resistance per linear foot of helium is about twice that of neon, and according to only half as many feet of helium tubing can be operated from a transformer as could be used if the tubing were neon filled. 24 Yellow and white colors, formerly obtainable only with helium, are now obtained from fluorescent tubes. 24 Argon, Krypton and Xenon. Argon ionizes with a very dim lavender color. Its light output efficiency is not great; so it is rarely used by itself as a light source in gas filled tubes. 1 Exam Prep Neon Techniques and Handling 4

5 24 Krypton produces a relatively dim but pearlescent white. It may become an important gas due to its lower voltage drop and its lower ionization potential. 24 Xenon is the heaviest of the inert gases and produces a thin, deep blue line in a clear glass tube Mercury Vapor. Mercury vapor is used universally used for practically all fluorescent luminous tubes. fluorescent tubes contain liquid mercury, which vaporizes under the proper conditions. 25 Rare-gas Mixtures. it has been found that the best gas mixture for all practical purposes is a mixture containing approximately 75 to 90 percent argon and 10 to 25 percent neon. 26 Cold Cathode Electrodes. Electrodes used for any type of luminous tube can be divided into two classes: the cold-cathode electrode and the hot-cathode electrode. The hot-cathode type of electrode is used in low voltage fluorescent lamps. Electrodes 27 Table 3.6: Voltage Drop of Neon-sign and Cold-cathode The electrodes supplied are of standard design and contain the following parts: [1-4]. 29 Electrode Requirements. To keep the cathode from overheating or sputtering excessively, three methods are used. The first and simplest The second A Third Lead-in Wires. Lead-in wires must be able to carry the sign current without heating, and they must have the same coefficient of expansion as the glass which they are enclosed. To meet these requirements, a special wire has been developed which is a copper-clad wire known as dumet wire. 32 Types of Seals. The most common method of making a seal for an electrode is the pinch external seal The glass is pressed between clamps over the lead-in wires and forms a vacuum-tight seal. 34 Insulation Materials. The method used almost universally today employs a mica shield. 34 Hot-cathode Electrodes. Hot-cathode electrodes can be divided into two classes: (1) (2). 1 Exam Prep Neon Techniques and Handling 5

6 35 Table 3-12: Fluorescent phosphors. 36 Glass Tubing. There are many different types of glass used throughout the world for signs and cold-cathode lighting, but in general these can be classified into two groups, soft glass and hard glass The soft glass group can be further divided into (a) lead and (b) lime or soda glass. In the hard glass group pyrex has been more commonly used. 36 As a rule, lead glass is used where tubing has to be bent or shaped. Lime glass tubes for lighting are used only where straight lengths are employed. 38 How Clear and Colored Glasses are Used. Fluorescent coatings or phosphor, colored filtering chemicals, are combined with the clear or colored glass to produce the many dozens of colors now in general use. 40 Production of sign tubing. The method used to produce fluorescent tubing is to coat the inside of the clear-glass tubing with a very fine layer of fluorescent powder. 40 there are factors other than the chemical composition of the powders which effect the ultimate color produced. These are: gas and the pressure used, diameter of the tubing, and the operating current through the tube. 41 Table 3.14: Clear, colored and examples of fluorescent-coated tubes 42 both the tubing and the chemicals must be kept free from dust and water vapor. Tubing should be kept and clean location. Electrical Equipment 44 Electrical Transformers. There are two general classes of transformers used with neon tubes,.the basic theory of step up transformer operation is similar in many of its aspects for both general types. 46 Tube Transformers. For luminous tube work a step-up transformer is required. 49 Transformer Ratings. Transformers are rated by (1) (7). All of the above factors must be considered in designing the sign installation. The transformer-output ratings vary from 2,000 to 15, 000 volts and from 10 to 200 milliamperes. 52 Power-factor Correction. Note entire section 1 Exam Prep Neon Techniques and Handling 6

7 58 Insulators and Mounting Parts. The elevation post, or tube support, is an insulator used in mounting the tube. 58 Figure 4.12: Electrode-insulator housings and bushings 59 Electrode Housings. 59 High-voltage Cable. the approved wire size is No. 14 copper wire. 60 Sign cable must withstand corona discharge Only standard high voltage cable specifically designed for luminous tubes should be used. The Types of Signs 62 Sign Backgrounds. A neon sign background must be designed to satisfy all of the following criteria It must be (1) (6) Outdoor Signs. 1. Projecting sign 2. Fascia sign 3. Outline border tubing 4. Roof sign 5. Pole sign 6. The Marquee Indoor Signs. 1. Skeleton sign 2. Indoor box sign 3. Window outline 4. Display sign 70 Figure 5.10: (a) (f) Letter Types. - Flat letter - Raised letter - Channel letter - Cut-out metal letter 72 Figure 5.11: (a) (d) 73 Types of Supports. - Swing sign - Upright sign - Fascia sign - Roof sign - Projecting sign 1 Exam Prep Neon Techniques and Handling 7

8 Designing the Sign 78 First an artist s preliminary sketch of the sign is made, more or less in detail but on a reduced scale. This sketch shows proposed location of transformers. Glass Bending 90 If the proposal is accepted by the customer, a complete mechanical drawing or working layout is drawn which gives details of every part of the sign including and connections. After the working layout is completed, the glass-bending patterns can be made from it The Master Pattern or Working Layout. it is recommended that the original layout contain the following items, either on the layout sheet itself or on specification sheets attached to it: (1)- (10) Designing the Tube. Note entire section 81 Table 6-1: Proper Gas Pressure for Sign and Cold-cathode Tubing Table 6.2: Transformer Footage Chart 88 Table 6.4: Power Ratings of Transformers 91 General Shop Requirements. The requirements for a wellequipped glass shop include the following: a supply of and the hand torch. These three constitute the required flames to bend and splice glass into whatever shape is required. 96 Gas-pressure Maintenance and Adjustment. The most common way of maintaining gas pressure at a constant value is by use of a booster or gas pump. 97 Air Pressure. Air at a pressure of one to two pounds per square inch must be mixed with the fuel gas to produce in the mixture required to give the proper flame. 97 Glass-blowing Equipment. Cross Fire. The burner most often used for glass bending. 98 Ribbon Burner. the ribbon burner produces a long ribbon of flame that is used to evenly heat sections Script letters such as O, C, G, B, R, etc. are all made partially on the ribbon burner. 1 Exam Prep Neon Techniques and Handling 8

9 101 The Mixer. A mixer is designed for a particular fuel gas...the heating value of fuel gases is measured in British thermal units (Btu) per cubic foot. 101 Glass Bending Layout. The glass bending layout is the actual pattern onto which the heated glass is set. The pattern is drawn as a mirror image from the back of the piece. 102 Patterns can be drawn on stiff paper or on a specially treated nonflammable cloth sold specifically to the neon industry. 102 To transfer a design to the pattern material several methods are used. The easiest is to transfer the artwork by use of an optical projector. 102 A second method is to draw on the original full-sized layout over a carbon paper covering the pattern material. The carbon paper deposits the reverse image on the pattern material. 102 Matching the layout. When the length of the tubing has been marked off, the bending begins, usually with the more difficult bends. As each bend is made, the bend is matched to the layout while the bend is still soft Splicing Tubing. Note entire section. 109 The Right-angle Bend. For a right-angle bend, the glass should be marked so that the portion of the surface placed into the fire will be two full diameters of glass. 109 Double-back Bend. The double-back bend is used for such letters as R, E, F, and G, where a complete 180-degree return bend is desired.the portion of the surface to be heated for a double-back bend is approximately 2 ½ to 3 times the diameter of the tubing Combination Bend. A combination bend involves two bends made at the same time from one heating in the fire. Many different types of combination bends can be made - Straight-drop combination - Combination-angle bend 111 Ribbon Burner Bends. A ribbon burner is used primarily to make long flowing curves. The glass is held and rotated approximately one inch above the burner. 1 Exam Prep Neon Techniques and Handling 9

10 When the glass becomes plastic the rotation then stops and the glass is moved from side to side until the proper temperature is reached for the circular bend to be made It is also important to allow the glass to completely cool before placing in the fire again. 113 The Tubulation. The tubulation forms an important part of the unit because all the impurities released from the unit during processing must be evacuated through it during processing. 113 The tubulation is sealed to the glass itself, it is usually placed at the rear of the glass unit so that the seal-off will be hidden when it is mounted in place. The tubulation is made like any other T-seal. 114 Figure 7.28: Sealing tubulation to glass letter 114 Working with Colored Glass. Colored glass made from sodalime glass has a higher working and annealing point than lead or other lead free glasses. 114 Colored glass should be preheated gently, 10 to 12 in. above the flame before bringing I down into the hotter portion of the flame. 114 Borosilicate (Pyrex) Glass. Borosilicate working temperatures are about 500 degrees F higher than lead glass and require gas/oxygen torches to work... which means that the two glasses will not seal together directly. 114 Borosilicate has the advantage in that since its coefficient of expansion is lower and can therefore be heated and cooled quickly with less fear of breaking. 115 Oven annealing. Annealing is the process of relieving strain by heating the glass to just below the softening point, called annealing temperature, and maintaining this temperature until the molecules can rearrange themselves into a stress free condition. 115 Glass should be kept at an annealing temperature for approximately 15 minutes and then allowed to cool to ensure thorough residual strain. Vacuum Systems 116 Vacuum Systems. The primary object of the vacuum system is to remove all the undesired gas and vapor from inside the tube. 116 The second objective of evacuation is to remove impurities from the walls of the glass and electrode shells. 1 Exam Prep Neon Techniques and Handling 10

11 116 Requirements for the Vacuum System. the following requirements of a good vacuum system must be met if good luminous tubing is to be produced: (1) (5). 118 Vacuum Measurement. The required vacuum for luminous sign tubing before filling is about one to five microns and for coldcathode tubing about 0.1 micron. 118 Relation between Pressure and Vacuum. as the vacuum increases, the pressure goes down Pressure of Inert Gas. If the pressure is too low (one millimeter or less), the tendency for the electrodes to sputter will be great. If the pressure is too high, the light output will tend to decrease and the resistance of the positive column will increase. 120 Pressures of 6 to 20 millimeters are usually used for luminous sign tubing. 122 Vacuum Manifold. The vacuum manifold is the part of the Vacuum system to which the tubes are attached for evacuation and filling. 122 Glass manifold systems can be made either with soft or Borosilicate glass. 122 In a lead glass manifold, the stopcocks used spliced to the rest of the system. 123 Figure 8-5 A: Neon Plant Schematic 124 Grease used for high vacuum stopcocks should have very low vapor pressure. 124 The main stopcock to the pump should have a plug with at least an eight to ten millimeter hole. Otherwise, it may interfere with the pumping speed. 126 Mechanical Pumps. The mechanical motor-driven pump can be used in either of two ways in the luminous tube pumping system. It may be used as the only pump on the system used with a diffusion pump or not. 126 The mechanical pump has two connections: the intake port and the output port The neon industry primarily uses belt-driven pumps because they run between 250 and 400 rpm versus 1725 for direct-drive pumps. 1 Exam Prep Neon Techniques and Handling 11

12 128 In general, a satisfactory pump for the average small luminous tube shop has a displacement of 15 to 40 liters per minute. 130 Diffusion pumps. Almost every manufacturer has some sort of high vacuum pump for high-speed pumping in the lower micron range. The diffusion pump, which works only below 100 microns, It works independently of humidity changes, pumping equally as well in wet and dry weather. It is extremely fast. It does not wear out since it has no moving parts 131 Diffusion pumps can be constructed either of glass or metal and either type can be air-or water cooled, depending on the pumps volume. 131 There are several other names for the diffusion-type of pump such as aspirator pump and condensation pump. 131 No diffusion pump should be opened quickly to atmospheric pressure while it is hot. 132 Vacuum gauges. The vacuum system must have one or more vacuum gauges. 133 There are two categories of gauges, direct and indirect reading gauges. Those measuring the force exerted on a surface Indirect gauges measure some property of the gas which is proportional to pressure. Gauges in the neon industry that use this property include the thermocouple vacuum gauge, and the Pirini gauge. 139 Troubleshooting. Another useful tool for detecting such a leak in a glass manifold or tube is the testing coil. This device is a transformer This tester, glows with spark discharge which causes any tube to with low pressure gas in it to glow. 140 Sealing the work to the vacuum manifold. (Entire paragraph) Bombarding 142 The importance of proper bombarding. Bombarding is the process of heating all the components of the luminous tube, both glass and metal, prior to or during evacuation. Bombarding serves several functions Heating of the gases also increases their kinetic energy, causing them to move faster, which aids in the evacuation of the tube, particularly at low vacuum levels. 142 Bombarding Equipment. The most common bombarding method used in luminous tube trade heats the tube with a bombarding transformer which provides a high voltage at a substantial current This transformer is connected to the tube while it is attached to the vacuum manifold. 1 Exam Prep Neon Techniques and Handling 12

13 143 The bombarding transformer may deliver currents as high as 2000 milliamperes on short circuit. 143 The bombarding transformer power is rated in kilovolt-amperes (kva) For proper bombarding, a transformer of at least 7.5 kilovolt-amperes is required. 144 Bombarding control. In order to control the bombarding current, There are three magnetic control devices which are commonly used for this purpose. - Tapped reactor/autotransformer - Choke coil - DC reactor 145 Bombarding layout. Figure 9.4: A typical bombarder layout 146 Bombarding procedure, simple case. When the proper temperature of the glass has been reached (250 vacuum pump stopcock is opened and the pressure reduced. 146 There are number of ways of determining the tube temperature An even better method is to use a thermocouple temperature instrument with a small probe. 146 For the average neon sign or cold cathode tubing, a temperature of 200 to 250 C is required for good heating. 148 Bombarding current. The bombarding current should start at approximately 200 milliamperes the intense heating current should be 600 to 750 milliamperes Overheating. Overheating has the following advantages: (1) (5). 151 The disadvantages are: (1) (4). Filling, Testing 154 Inert gas containers. There are two types of containers used in Aging the neon trade to hold inert gases, metal cylinders and glass flask. 154 Glass flasks usually hold 1 to 2 liters of inert gas at atmospheric pressure Glass flasks come in both lead and borosilicate glass and all the inert gases are available in both. 154 Metal cylinders are available to hold hundreds or thousands of liters of pure gas. 155 Table 10.1: Degree of vacuum by color, using spark-coil tester 1 Exam Prep Neon Techniques and Handling 13

14 158 Measuring the inert gas pressure. When the tube has been evacuated to the required degree of high vacuum (five microns or less) When the desired pressure has been reached, the stopcock is shut. 158 Filling tubes hot. It s not necessary to wait until the tube cools to room temperature before filling as long as the operator is sure that the tube is thoroughly evacuated. 158 Filling tubes at temperatures significantly above room temperature requires the use of Boyle s Law. 159 Table 10.2: Hot filling chart 159 Testing the tube. To test the tube the most common method is to set the bombarder the tube probably can be sealed off. 159 Sealing off the tube. (Entire section) 161 Methods used for mercury insertion. The two most commonly used methods for inserting mercury into a tube are by use of a mercury trap, or the injector method. 161 The mercury trap. A mercury trap can be made in several ways. The simplest way is to attach a short length of 5 mm tubing The advantage of this method is that it is relatively simple to use. 162 The mercury injector method. The mercury is inserted into the ball on the end of the rotatable piece the trap is rotated 180 degrees to permit the clean mercury to flow directly into the tubing. 162 Figure 10.4: A manually operated mercury injector Quantity of mercury necessary. (Entire section) 163 Flow-through filling. an alternative method for evacuating a filling a tube is by using two tubulations, one on each end of the tube. One end of the tube is connected to inert gas supply and gauges. 164 Aging methods. (Entire section) Complete Luminous- 169 The shop-assembled sign. For signs built on metal boxes the tube Sign most commonly used mounting for the glass tubing is the the support holds the tube in place and provides the structure to hold the electrode against the spring in the electrode housing. 1 Exam Prep Neon Techniques and Handling 14

15 169 To provide electrical connection to electrodes, a box sign may use either an electrode receptacle, such as a housing, or a ring bushing. 169 The ring bushing merely insulates the glass electrode from the metal box. 170 Figure 11.2: 171 Installation of transformers. Unpainted, galvanized sheet metal or plain aluminum transformer boxes are poor heat radiators. A transformer in such a box can run as much as 30 degrees F hotter than in the same transformer box which is painted. 172 Skeleton-type signs and mountings. The skeleton-type sign is usually self-supporting; that is, it is not solidly fastened by means of elevation posts 173 High-voltage wiring general practice. (Entire section) 175 Figure 11.6: Load testing transformers using milliammeter method Correct loading of transformers. The load testing methods are: (1) (5) 177 The second type of test (see Figure 11.6) requires a milliammeter to be connected to two ends of the transformer without the tube load. 177 The third method requires the use of a digital voltmeter equipped with a high-voltage probe. Flashers and 184 Mechanical animators: primary vs. secondary flashing. Animators (Entire section) 184 Thermostatic primary switches. The simplest type of mechanical primary switch is the thermostatic blinker used for simple on and off switching of a complete sign. 184 the transformer load connected to a typical thermostatic flasher must not exceed 100 volt-amperes. 185 Motor-driven primary flashers. This type of primary mechanical flasher is used for more precise timing and when multiple circuits need to be animated. 1 Exam Prep Neon Techniques and Handling 15

16 185 The drum and brush flasher is capable of handling load up to 1000 watts per brush The camshaft type rotary flasher is illustrated in Figure 12.2 Loads up to 3000 volt-amperes per contact may be handled with this type of flasher. 187 Secondary flashers: rotating gap type. One type of secondary flasher is the rotating gap type 187 The contacts may be used at any voltage up to 15,000 volts. 188 Electronic Animation. Electronic switching allows large numbers of neon tubes to be animated and controlled by programming sequences of flashing through sophisticated lighting control software. 189 A cross fader is a type of electronic dimmer control used for multiple lighting circuits. Radio and Television 192 Designing signs with lower voltage transformers, preferably 9000 Interference volts and under Overloading transformers is one of the major causes of interference in a neon sign. 192 Electrical interference can be either of, or a combination of, two types of interference: that which travels through the AC line, or interference which is broadcast through the air. 194 The general steps for eliminating an interference problem are: (1) (3). Sign Maintenance 198 Causes of service calls: Tubing failures. There are two places where a sign may fail; in the transformer and its connections, and in the tube itself. 199 Tubing repairs and replacements. Solarization is the result of long-term bombardment of the glass by the ultraviolet portion of the neon light. This energetic radiation changes the glass causing it to darken.the only way to eliminate solarization is to strongly heat the glass close to its annealing point in the oven Table 14.1: Neon Tube Darkening Troubleshooting Guide 203 Electrical failures. A transformer usually fails due to an internal breakdown of the insulation. Heat and moisture are the chief causes of such a breakdown. Loading condition also effect a transformer. 1 Exam Prep Neon Techniques and Handling 16

17 204 Flasher failures. When the flashing devices of a sign fail, there is usually no remedy but the installation of a new flasher. 204 Maintenance guarantees. As a rule, this is for one year. Safety 210 Mercury. Exposure to mercury is divided into two categories, acute and chronic. Specialty Neon and 214 Lighting Displays Index Steps that can be taken to minimize mercury exposure include the following: (1) (10). 211 Carbon monoxide and carbon dioxide. byproducts of operating the glass fires. 212 Hydrofluoric acid. HF is the most powerful acid known HF should never be breathed or allowed to touch the skin. 1 Exam Prep Neon Techniques and Handling 17