Trouble Shooting Sign Lamps
An easy way to check your lamp and ballast operation

Lamp Life

Lamp life is expressed in avenge 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 mean 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 may determine the group-relamping interval.

Repeated Lamp Outages

Repeated lamp outages in a particular sign are a strong indication that the problem lies elsewhere than in the lamps. Something wrong 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.

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 may 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. This can occur anytime. A gray band about 2 inches from the end of the lamp which normally appears in fluorescent lamps toward the end of lamp life.
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, may 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 tester does not light, replace the ballast, as it is not developing filament-heating voltage. If there is light and 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.