TUFBEND® U-Lamps do not have to be installed with uniform spacing between lamps to achieve uniform sign-face illumination. For normal painted sign faces, and most rigid plastic faces, the maximum recommended spacing shown on the table 2 below will provide excellent uniformity of illumination.

As you can see on the table below, for signs with flexible film faces, lamp spacing is greater than with plastic face signs, thus the same sign can be lit with fewer FTU-lamps.

To achieve balanced lighting in signs 12 inches deep or more, space FTU-Lamps further apart to create a diffused, even effect. In narrower signs, space FTU-Lamps closer together to eliminate “hot spots” or dead gaps.

As with all fluorescent lamps, care should be taken in handling TUFBEND U-Lamps to avoid breakage. Users of TUFBEND U-Lamps can save money by following the procedures outlined below to ship signs with the lamps already installed.

FAQs 1During sign shipment, particularly when lamps travel horizontally, the best way to protect the lamps is by simply looping hard twine or tie wire around lamp mid-points, as in the sketch. Cut and discard at first relamping. Permanent cushioned supports may be used instead, but are generally unnecessary.

“Whip” Prevention

When signs with lamps in place are likely to be treated roughly during shipment, or when the sign might be installed under extreme conditions involving heavy vibration, rods or lamps should be restrained. This protection should be undertaken to prevent “whipping” (Fig. 4) and the possibility of lamps striking sign faces or structural elements. The longer the lamp and rod, the more important this becomes.

A structural member or specially provided support can carry a bracket to restrain whip. A “U”-bracket formed from 3/4″ wide aluminum strip can be pop-riveted to a structural angle and the rod in turn is pop-riveted into place in the bend of the “U.” (See Fig. 5.)

Another option is to stretch wire across the lamps, just touching them, about 8″ from the bends. Rods are tied to the stretched wire with lighter-gauged tie wire. Hook openings should face stretched wire so its force tends to keep lamps in the hooks. Figure 4 & 5

Lamp Retention in Mount

When very rough treatment of the sign can occur, it is best to positively retain U-Lamps in their mounts so they cannot jump out under heavy jolts. (Fig. 5)

Install cotter pin in rod hole as shown. Run the wire through the eye of the pin, and twist around the ends of the hook. Cut and discard wire at first relamping. This prevents the spring in the rod from compressing under a jolt and releasing the lamp. Hole and cotter pin are provided with all rods.

U-lamps are installed using Voltarc mounts, shop-fabricated hardware or a combination of these techniques:

Standard Mount for Double-Faced Signs

  • Standard Base – is complete with sockets. Specify U6-HO, U9-HO or U6-SL according to lamp type. When using U6 or U9-120/HO lamps, specify U6-120/HO or U9-120/HO bases which have special light follower springs on sockets to help insure good electrical contact
  • Closure Plate – has knockout. Optional, two needed if used. Encloses base end to UL standard. Fits all Voltarc bases
  • Rod – Has captive spring-loaded double hook. Specify U24 through U120 according to lamp length. U6 and U9 lamps use same rod; for example, U6-72 and U9-72 lamps both take U72 rod.

Installing Mount and U-Lamp

  1. Attach base to frame of sign. Mounting holes are provided.
  2. Wire sockets in accordance with ballast wiring diagram. If UL standards are to be met, use either flexible or rigid metal conduit clamped to closure plate knockouts, or connect bases with shop-fabricated hat sections. Note: wiring might be done as Step 1, before base is attached to sign.
  3. Attach closure plates, if used, to the base. Holes will take#8 blunt-end sheet metal screws or 1/8pop rivets
  4. Insert rod through two large base and bridge holes, align small hole near end of rod with two small holes in sloping sides of bridge.
  5. Insert locking cotter pin, furnished with rod, through both small bridge holes and small hole near end of bridge
  6. Insert lamp ends in sockets. Make sure lamp bases seat properly.
  7. Pull hook clear of lamp bend. Use two fingers under hook crossbar. Do not exert thumb pressure on lamp. Tilt lamp into hook.
  8. Release hook onto lamp. Do not let it snap onto lamp, release it gently.
  9. Wire lamp in place as shown for positive retention during sign shipment.

Tombstone Mount for Single-Faced Signs and Letters

Tombstone mounts make it easy to light large letters and single-faced signs by positioning U-Lamps parallel to the mounting surface. The Tombstone mount consists of a Tombstone Base which is furnished complete with lampholders. Also required are a Rod Bracket and a rod.

1. Attach the base to back of sign or letter. Wire sockets and attach closure plates, if used.

2. Attach the rod bracket along lamp centerline. The distance “D” from the base varies with lamp size. See Fig. 1 and Table 1.

3. Insert 4 1/2″ ROD through the large holes in the bracket.

4. Insert the locking cotter pin furnished with the rod through the hole near the end of the rod. Spread the pin legs.

5. To install the lamp follow steps 6-9 as with standard mount.

NOTE: A ballast can be mounted between lamp legs on all but the shortest lamps.

Shop-Fabricated Mounts

It might be economical to employ shop fabricated or extruded raceways and utilize VOLTARC rods when signs are produced in quantity.

THE RODS SHOULD BE POSITIONED so that the hook crossbar is extended out 7/8″ from the supporting tube with the lamp in place. This positioning is automatically correct when VOLTARC bases are used. (See Fig. 5.) Rod support holes should be .635″ in diameter for the most rigid construction. The rod nominal diameter is .625″.

FOR SINGLE-FACED SIGNS, shop-made raceways can be used with the VOLTARC Rod Bracket and 4 1/2″ rod shown in the section above on Tomb-stone Mount. The lamp centerline should be about 2 1/2″ from the back of the sign to match the elevation provided by the rod and bracket. No direct connection between the raceway and the bracket is needed, when proper spacing is maintained.

CONTINUOUS WIRING CHANNELS can be made by using shop-fabricated hat sections to connect VOLTARC bases. Choose the length according to the spacing between adjacent bases. Allow a 2 3/4″ by 1 1/4″ cross section. See Fig. 1. Where connecting hat sections are used, VOLTARC closure plates are not needed.

  1. TUFBEND U-Lamps are packed 6 per shipping carton in boxes carefully designed to minimize breakage during shipping and transportation to the job site.
  2. The patented integral stabilizing brace employed in lamps FTU-60 or longer further reduces the likelihood of breakage.
  3. TRUCK STORAGE OF TUFBEND U-Lamps is best handled simply by leaving lamps in their shipping cartons. Simply deploy a shop-built sheet metal storage box with plywood dividers and keep a bill of materials listing the original components designed into the sign on file. When the sign requires relamping, a check of the file will show which TUFBEND U-Lamps were originally used.
  4. INSTALLING TUFBEND U-Lamps. Pull the hood clear of the lamp bend by using two fingers under the crossbar of the hook. Avoid exerting thumb pressure on the lamp. Lower the hook gently on to the lamp. Do not snap into place.

An easy way to check your lamp and ballast operation

Lamp Life
Lamp life is expressed in average rated hours. This is defined as the median life of a large group of lamps operated under laboratory test conditions on a 3-hour on, 20-minute off cycle. Laboratory test conditions means controlled room temperature, selected reference ballasts, correct voltage and, in general, ideal conditions. Under these ideal conditions, 50% of the group of the lamps will have failed prior to rated hours of life.

In signs, conditions are far less than ideal. Considering the cost of service calls, and the poor appearance of signs caused by burnouts, it is often desirable to group-relamp at 18- to 24-month intervals on a basis of pure economy. If there is a regular cleaning schedule requiring a service call, this might determine the group-relamping interval.

Repeated Lamp Outages
Repeated lamp outages in a particular sign are a strong indication that the problem lies somewhere other than in the lamps. If something in the sign is causing the lamps to fail, the following troubleshooting routine will help you to locate and correct the cause of the lamp failure as simply as possible.

Troubleshooting Routine for Signs Using HO Lamps
Equipment needed:

  • A filament heating voltage tester, available from Voltarc
  • A volt-ohmmeter with probe leads, or a voltmeter and a pen-type continuity tester with pin-prick probe and alligator clip
  • Known good lamps to fit the sign

Steps to Follow to Determine the Nature of the Problem in a Sign That Does Not Light 

  1. Visually inspect the lamp ends. If one or both lamp ends have heavy solid darkening 2 to 4 inches long, after a short period of operation, this indicates lack of proper filament heating voltage. And, while a new lamp might light in the lampholder, it will have a short life. Do not confuse this type of end darkening with small dense spot near the end of the lamp, which is a mercury deposit – a gray band about 2 inches from the end of the lamp which normally appears in fluorescent lamps toward the end of lamp life. This can occur anytime.
  2. Visually check for and replace ballasts, which have leaked compound or have been water soaked.
  3. Check primary voltage. Assuming 120-Volt service, 110 to 130 Volts must be present. If not, this must be corrected before proceeding.
  4. Check that the sign casing is properly grounded. There should be no voltage between the sign casing and the primary lead of the ballast and full voltage between the sign casing and the black primary lead of the ballast. A sign, which is not properly grounded, might cause confusion during trouble shooting, as well as being a potential hazard.
  5. With power on, check all sockets for proper filament heating voltage by inserting a filament heating voltage tester. Tester bulb should burn bright. Wiggle tester in lampholder. It should remain lit. Pay particular attention to locations where lamps showed solid end darkening as this is most commonly caused by inadequate filament heating voltage. Check for broken or corroded contacts or evidence of moisture in the lampholder. If the problem is visible, cut off power and replace the lampholder. Recheck with power on.
  6. If the filament heating voltage tester lights dimly, or fails to light, locate the two ballast leads of the same color as those at the lampholder. With power off, cut and strip leads near the ballast. With power on, apply the ballast’s leads directly to the filament heating voltage tester. If the tester does not light, replace the ballast, as it is not developing filament-heating voltage. If there is light, an open circuit exists at some point in the sign wiring. Trace wiring, repair and retest.
  7. If all lampholders show filament heating voltage present, and lamps which are known to be good won’t light, shut off power and disconnect both ballast primary leads.
  8. With continuity tester, or with ohmmeter on “low ohms” scale, check all ballast secondary leads for “short” to ground. A short will give a low reading on the ohmmeter or light on the continuity tester. This can be done at the lampholders by checking both contacts, or by a pinprick probe making contact with each ballast lead wire by puncturing the insulation.

This troubleshooting routine will establish:

  • If primary voltage is OK
  • If filament heating voltage is OK
  • If there is no short to ground and no open on any leads
  • If lampholders are OK

After running through this troubleshooting routine, if known good lamps fail to operate, the ballast is failing to provide high voltage and must be replaced. This troubleshooting routing is absolutely foolproof, and will enable you to locate and repair any electrical problem in any sign.

There are various types of darkening that occur with lamps, and each type of darkening is associated with certain specific causes. The ability to recognize the different types, and to understand the causes, make it possible to correct imperfect conditions and to employ procedures that will best solve the problem. This Technical Bulletin will describe in detail each type of darkening, along with its causes and remedies. It will also discuss sign tubing components and equipment as they affect darkening.
It is possible that a tube experiencing darkening could have several things wrong with it at one time. Sometimes these faults can be recognized individually and sometimes not. Most types of darkening are stains, which start out light in color and gradually darken and spread with age. Different kinds of strains tend to look more and more alike as they get older. Therefore, identification of the various types is much easier when tubes are new than when they are old.

Having said that, we will discuss different kinds of strains here under the assumption that each one is happening in isolation, without other forms of strains happening at the same time.

Specifically, we will explore the following situations:

Darkening Around and Next to the Electrodes:
There are at least three different kinds of darkening occurring at the electrodes. They can easily be differentiated by their color when the tubes are new and, with more difficulty, by color and extent when they are older.

The first kind is called sputter, and it appears either as a black spot or ring just in front of the electrode, or anywhere on the electrode glass. It is mainly a metallic throw-off from the electrode shell. During the life of the tube, it might extend a distance of two-to-three inches from the electrode, into the tube. It might also extend back toward the electrode press, covering all of the electrode glass. The end of the dark area away from the shell is usually fairly well defined.

Sputter might appear during or after bombing. When it occurs during bombing, it is caused by over bombing (by heating the electrodes too hot, for too long a time, at too low a pressure, at too high a current.) If it occurs after bombing, the conditions above might still have been the cause, but  there are other possibilities. The reason might be low-filing pressure, operating the tube on a current higher than the design limit of the electrodes, the use of uncoated electrodes or of electrodes having an inadequate supply of emission coating. Old tubes normally show some electrode sputter, and this is to be expected. Ordinarily the well-processed tube should show a little or no sputter during the first few hundred hours of operation.

The second kind of darkening staring from the electrode gives the clear glass a greenish color when the tube is lit. It might be yellowish or brownish when the tube is not lit. It starts just at the open end of the electrode shell, and the edge of the stain at the end away from the electrode is generally somewhat diffused. As the staining grows older, its color becomes darker. It creeps farther and farther away into the tube, covering the coating and preventing it from fluorescing. It can eventually cover the whole tube.

This stain is associated with the emission coating and never appears when uncoated electrodes are used. Electrodes that have uncontrolled weights of emission coating are particularly difficult to bomb and tend to produce this kind of stain. Emission coatings that are completely and properly converted do not produce it unless they become contaminated.

Conditions that cause the emission coating to produce this stain are as follows

  • Incomplete breakdown of the emission coating during bombardment
  • Under heating and/or incompletely degassing the emission coating and electrode shell (similar to above.)
  • Poisoning of the emission coating or absorption of impurity gases resulting from an inadequate pumping system

> The presence of water vapor
> Inadequately-heated glass on the pump
> Contaminants in the tube or pumping system
(No other stain appears as frequently as this one. The cure lies primarily in bombing procedures.)

The third type of stain appearing at the electrodes is a grey cloudy formation extending varying distances into the tube. It is caused by vaporizing mercury out of or off an electrode. The vaporized mercury condenses on the nearest cool surface, forming the grey cloud. For this reason, mercury should not come in contact with a hot electrode. Rolling mercury in and out of an electrode can sometimes produce a black streak of contaminated mercury on the tube wall. (See section V) The grey cloudy stain might disappear or over as the tube is operated.

Darkening Starting a Short Distance Away From The Electrode:

There are four kinds of stains that fit this description. Three can be serious, although the fourth is generally unimportant.

  • The first kind is associated with ceramic-type electrodes and takes the form and color described in the first section. It is different only in that there is a clean area between it and the electrode when the stain is new. As the tube grows older, the stain might extend itself in both directions and close the original gap between it and the electrode. The edge of the stain at the end away from the electrode is diffused. It has the same cause and remedy described in the first section. It appears that when this kind of stain first forms, the ceramic focuses the stain a little farther away than does the non-ceramic electrode.
  • The second kind of stain, starting two or more inches away from the electrode, can cover an area of 6 to 8 inches in length or, when it gets very bad, the whole length of the tube excepting near the electrodes. It might start out as a light discoloration, and at times can become completely black with age, although it will not always do so. There is a definite line of demarcation between this stain and the clear area adjacent to the electrode. The edge of the stain at its end away from the electrode is indeterminate. This stain is caused by moisture in the tubing or in the pump system.
  • The third kind of stain has an appearance similar to the one above and is produced by small amounts of air in the tube. The air stain, however, has a fairly well-defined edge at both ends. It might move from one section of the tube to another and might finally even disappear altogether. If a moving stain appears, it would be wise to check the vacuum system for leaks. A large amount of air will cause the tube to run very hot. The whole tube is likely to darken.
  • The fourth kind of stain at this location is a dark ring, which is generally quite narrow. It appears about 1 to 1 ½ inches away from the electrode splice, and might also appear on both sides of other splices and next to bends. The stain, which occurs right on the splice or bend, is described in Sec. III. In tubing containing calcium silicate (pink or Ca-Whites) the ring sometimes has a pink color. In green tubing, it might be a lighter green than the rest of the tube. Generally, however, it is dark grey. In itself this discoloration is quite innocuous, and it does not become worse with age.

These rings are produced by locally heating moist tubing and by allowing combustion products from the fires to enter the tubing. The number of rings appearing can be reduced greatly by making bends only on tubing that is completely dry, and by making splices only after the bends have completed. If moisture can be kept out of the tube, no ring will appear.

Dark Bends and Splices:

Bends and splices might develop a discoloration, which starts out grey in color and later turns black. In extreme cases, this darkening might be seen before pumping, but usually not until after pumping and operating the tube. Only the heated area of bends and splices, and up to half an inch or so on either side, is affected. It occurs mainly on tubing containing tungstates (blue powder) or halophosphates (white powder). For practical purposes, this means that any blue or white tubing (whites might contain either tungstates or halophosphates or both). For dark rings near the bends and splices, see section II, the fourth kind, above.

This discoloration is caused by overheating the glass when working it in the fire. Gentle heating prevents it. The glass should be heated only enough to make a strong splice without much “melting in,” – just enough to make bends without kinking.

The discoloration on bends and splices in glass that has been heated too much can be reduced greatly by running clean water through the tubing before the electrodes are attached. A few minutes of full flow suffices. (A water flow that is too forceful might wash the powder out of the tube). The tubes must then be IMMEDIATELY and THOROUGHLY dried by flowing air through them before attaching the electrodes. Oven drying is helpful, but it should not be attempted before drying with the air. If the tube is still moist when it is put into the oven, a number of small spots will appear. Water washing will reduce the brightness of the halophosphates tubing to some extent, and is therefore recommended only for those cases where it is known that too much heat has been applied.

Darkening Covering the Whole Tube:

The whole tube might look grey, brown, a depressed yellow or black. The discoloration might be uniform over the whole length of the tube, or there might be an area of normal brightness located near the middle. (See Sec. 2, third kind).

This darkening sometimes looks like the dimming that results from lack of mercury vapor. One can determine which it is by heating a small section with a torch and watching the change in brightness. If only this section brightens, the tube is stained. If brightness develops and extends some distance beyond the heated area, it is caused by lack of mercury.

Darkening of the entire tube might also be confused with other low-light output conditions. If the tube has a uniform low brightness without any evidence of stains, it is probably just old. Tubes operated on an over-loaded transformer also might look dim and stained when they might be merely operating at a reduced current.

If the condition actually is a darkening or staining over the whole length of the tube, it can be caused by a number of different things. These causes are listed below in order of decreasing probability:

  • Poor vacuum conditions. Either a slow pump or a large air leak in the manifold can cause this kind of staining. Wet tubing can also do it by slowing down the pump and/or by contaminating the emission coating.
  • Inadequate electrode bombarding.
  • Glass not heating sufficiently during pumping. This can be particularly troublesome when using no-bake tubing.
  • Too short a pumping and bombarding period
  • Contaminated mercury
  • Contaminated tubing. Again, no-bake is difficult to process.

Irregular Dark Patches:

Darkening of this kind takes the form of stains of irregular sizes and shapes, color and locations. This group includes those stains that do not ordinarily cover the entire circumference of the particular area in which they are located. Foreign matter in the tube usually causes stains such as these.

  • Poor vacuum conditions, either a slow pump or a large
  • Bits of rubber give small roundish stains with a definite darker center. They are frequently yellow.
  • Small pieces of emissions coating make small irregular blotches. They are generally yellow or grey, but pieces, which fall into very hot fluorescent coating, might turn blue.
  • Oil might produce regular or irregular shapes and colors. It can also produce a light yellow stain going all the way around the tube and extending for a large distance. It is likely to turn black. (The oil might come from the splicing fires, the diffusion pump, stopcock grease, oil manometers or “gremlins.”)
  • Mercury collects around cold spots in a tube, such as near tube supports, and makes small but unsightly dark areas. Its effect on the fluorescent coating might be the same as described below.
  • Moisture in a tube can produce some strange looking bands/streaks. These are usually quite narrow and are done essentially the same as described in Sec. II, fourth kind. If narrow, they apparently cause great harm.
  • Mercury, contaminated by contact with an over-bombarded electrode or hot electrode, might produce a number of very thin black streaks up to several inches long which are generally harmless. Sometimes the streaks might be as wide as one-quarter inch, in which case there can be a serious appearance defect.
  • Stains shaped like half-moons and located close to the electrode are caused by over bombing. They seldom become serious.
  • Heavy clusters of mercury droplets, sometimes in the shape of a large teardrop, have also appeared in connection with over-bombarding. The teardrops are usually a minor appearance defect unless the concentration of mercury is heavy. In such cases they might lift the fluorescent coating off of the glass, leaving bare spots.

In most cases, the cure for darkening is almost entirely a matter of bending, splicing and pumping technique. The types mentioned here, as well as any number of others, are preventable given the right approach.

Voltarc 9-foot and 10-foot lamps should be used whenever their use substantially reduces the number of lamps that would otherwise be needed.

Standard in every way, Xtra Long lamps are used exactly like any other straight HO lamp. Ballasts to carry up to four F108, F117 or F120T12/HO lamps are offered by all sign ballast makers.

Starting aids should be provided to help in reliable lamp starting when temperatures are low or humidity high. For double-faced signs, a grounded strip of metal stretched the length of the lamp serves as the starting aid; ½” wide and ½” away or ¼ ” wide, ¼” away are acceptable. For single-faced signs, the metal back will normally serve the purpose.

You can achieve uniform illumination across all dimensions of the sign and reduce overall manufacturing costs.

  • You need fewer TUFBEND® U-Lamps than straight lamps to light the sign, providing you with a material and labor cost savings
  • Access to the sign for servicing is easier with only one raceway
  • You can light large letters and irregular shapes easily; i.e., large channel letters, ovals, circles, etc.

A TUFBEND® U-Lamp can provide uniform illumination for any non-rectangular or odd-shaped sign, regardless of configuration.

  • No lighting gaps
  • No shadows
  • Shadowless light in curved areas
  • Backlit Awnings – TUFBEND® U-Lamps provide uniform illumination with no dead spots at the end of the awning

U-Lamps will give shadowless lighting in curve areas and can be used in combination with straight lamps.

Cold-Cathode fluorescent lamps (CCFL) use a cylindrical metal shell (electrode) coated on the inside with emission coating.  A cold cathode is distinguished from a hot cathode in that, unlike hot cathode lamps that are heated to induce thermionic emission of electrons, cold-cathode lamps are not.  The interior surface of cold cathodes is capable of producing secondary electrons upon electron and ion impact. For acceleration of the ions to reach a sufficient velocity for creating free electrons from the cathode material, cold-cathode discharge lamps need higher voltages (and therefore lower current) than hot-cathode lamps.

Hot-cathode fluorescent lamps (HCFL) use a tungsten filament typically covered with an emissive layer, made of a material with lower work function, which emits electrons more easily than bare tungsten metal, reducing the necessary temperature and lowering the emission of metal ions and heated to orange-hot.  The filament can be either directly heated, where the filament itself is the source of electrons, or indirectly heated, where the filament is electrically insulated from the cathode.  Hot cathodes typically achieve much higher power density than cold cathodes, emitting significantly more electrons from the same surface area resulting in higher output and can operate at higher lamp currents.

U-lamps should be used to light signs when their usage increases your profit making opportunity on the sign or improves illumination. These twin goals might be reached in several ways:

  1. Achieve Manufacturing Cost Savings
    • One TUFBEND® U-lamp does the work of two short straight lamps. Fewer ballasts and sockets must be purchased and installed.
    • Lamp ends are only inches apart in one raceway, not separated by feet.
    • Single-ended lamp support means less raceway work.
  2. Keep Sign Maintenance Responsibility
    • Voltarc U-lamps are universally available in the USA and Canada from electrical sign supply distributors.  They are not available from conventional electrical wholesalers.
  3. Help Solve Tricky Lighting Problems
    • U-lamps can often simplify sign construction of non-rectangular shapes since they require support at only one end. They provide adequate light from the opposite bent end.
    • Bent lamps will give shadowless lighting in curved areas and can be used in combination with straight lamps.
    • Regardless of configuration, a U-lamp can provide illumination for any non-rectangular or odd-shaped frame – such as a cowboy’s hat, a torch, an odd-shaped letter or a giant cactus.

Using fewer lamps reduces labor costs, as well as sheet metal work and wiring. It also reduces the number of ballasts and sockets that need to be installed and maintained. The overall result is cost savings as well as simplified maintenance and better performance.