Lamp Handling Tips and Remedies


When purchasing lamps, always check the manufacturer's specifications and UL listing for the lighting fixture. Just because a lamp will fit doesn't mean you can use it!

The following problems and suggestions cover some of the most common problems and solutions. This is not a list of every possible problem or solution. If you have questions not answered below or if you have suggestions please contact our technical support by phone at 336-882-2854 or by email.

Problems and Possible Solutions

Lamp burns out before end of life
Lamp turns black
Large bubbles swell up on the bulb
Lamp base cracks or breaks
White haze on the glass
Varying resistance across lamp
Changing lamps too often on large lamp installations
Variations in color across a series of lamps
Unexpected lamp burst
Broken or melted filaments

Handling Tips

How to extend your lamp life
Shock and Vibration
Switching Projector On and Off
Cooling
Line Voltage Power
Lamp Installation

Lamp burns out before end of life

Line voltage lamps may be subject to power swings. Check line voltage. Minimize power swings to less than 10%.  Try using a 130V version of your bulb in 120V applications and using a 240V version in 220V applications if you are having line voltage problems.

Low voltage applications will fail prematurely if the voltage regulator is sending too much voltage to the socket. Check voltage with lamp in place.

Oil from fingerprints, nasal tissue or other sources on the glass will cause premature failure with halogen, xenon, and high wattage incandescent. Use gloves or a clean cloth to handle lamps.

Under cooling caused by blocked or failed cooling systems. Keep filters clean and area around equipment free from objects that might restrict air flow or create heat.

Damaged sockets will cause short lamp life. If the socket contacts have pitting or corrosion causing inconsistent lamp current it will shorten lamp life. Replace damaged sockets.

Short on/off cycles can prematurely damage high wattage lamps. For example, if you are running a slide or film projector a good rule is that once you turn the lamp off, leave it off until it cools before moving the projector, jarring the projector in any way, including the applications of electricity. Filaments are more brittle, so easier to break, when hot.

Lamp turns black

Is the lamp over cooled?  Direct airflow on the bulb can cause the lamp to turn dark. Minimize cooling to match equipment design requirements.

Toward the end of a lamps life some black is normal as the exhausted filament collects on surfaces.

Large bubbles swell up on the bulb

May also be related to over cooling.  Dark spots that have collected on the bulb will absorb heat then the quartz may bulge.

Oil from fingerprints on the glass can quickly cause glass to bulge when it gets hot. Bulges are fairly common with high wattage, incandescent projector lamps.

Lamp base cracks or breaks

Often related to improper installation and removal of lamp or a damaged socket. Check and maintain the sockets. Are they oxidized, pitted, burned, bent and/or dirty? Periodically replace sockets. 

White haze on the glass

May be silica haze or smoke. Generally not a problem and most often is silica left over from the production process.

If there is a vacuum leak caused by improper installation, shipping damage or a failure of the manufacturer to apply a proper vacuum the lamp will usually fail as soon as oxygen gets to the burning filament. A vacuum leak failure will leave a white or greenish-white powder in the lamp.

Varying resistance across lamp

Most of time this is humidity related. Small amounts of moisture can collect in the base of some lamps.

Changing lamps too often on large lamp installations

It is very important to change all the lamps on large circuit strings at the same time. Lamps all have some sort of average life. Should you just change a few lamps at a time as they burn out, you may later find a whole series failing, usually at an inopportune time. These additional lamp failures may be simply related to the fact that they have reached end of life. You can date lamps when you install them if you do not change all the lamps as a group so you have an accurate idea how long they are lasting..

Variations in color temperature across a series

Make sure the voltages to all the lamps or strings of lamps are consistent. Power variations can cause some lamps to operate above or below rated color temperature.

Make sure all lamps are of the same design. Aluminum reflectors will present a different color than dichroic reflectors. If you have aluminum lamps and add a dichrioc you may say the dichroic looks pink or if you have dichroic lamps and add an aluminum lamp you may say the aluminum looks yellow.

Fluorescent lamps are available in a variety of color temperatures. Make sure all lamps are rated for the same color temperature and ideally replace all lamps as a group with the same brand at the same time.

Unexpected lamp burst

Never handle lamps with bare fingers. Inspect the bulb for accumulated dust or dirt. Wipe the bulb as need be with alcohol and a lint free cloth.

Do no turn high wattage lamps on and off in short sequences. A good rule is that once you turn the lamp off leave it off for at least ten minutes with the fan running before you turn the lamp back on.

Broken or melted filaments

Make sure the lamps do not encounter serious vibration. Filaments are more brittle when hot. Even if the lamp is off and still hot a jar can break the filament. Jars to the filament include physically jarring the projector or surface supporting the projector and the applicaion of electricity.

When changing quartz lamps, be careful not to touch the quartz glass surface with your skin. This can decrease the lamp life and/or discolor the lamp during use. 

When changing, hold a quartz lamp with the paper included with the lamp.

Any bulb more than 150 watts has a CYCLE time, 10 min on then 10 min off.

How to extend your lamp life

Lamp failure occurs due to a mechanical break in the tungsten filament winding. As the lamp operates the tungsten filament becomes thinner due to evaporation and it eventually breaks. Failure may be accelerated by factors such as, mechanical shock, vibration, high line voltage and temperature.

Shock and Vibration

Lamp failure in an overhead projector can be due to mechanical shock. This occurs when using the lamp changer or bumping the unit while the lamp is operating. A hot lamp filament is very fragile. You should always make sure the unit is turned off and the lamp is cool before moving the lamp changer or the unit.

Switching Projector On and Off

Each time you turn the unit on, there is an inrush current that applies stress to the lamp filament. The more often this stress is applied the sooner the lamp will fail. For this reason, turning the overhead projector "on" and "off" frequently during presentations is not recommended. Some projectors have a "soft start" power supply that provides a gradual voltage increase which limits the inrush current shock. This results in extended lamp life.

Cooling

Improper cooling can cause lamp envelope seal failure or lamp capsule swelling. Always make sure the fan is operating and the intake and exhaust vents are not blocked.

Line Voltage Power

High power line voltage is a major cause of short lamp life. Using a voltage less than the rated lamp voltage will increase lamp life but, reduce light output. Higher line voltages will reduce lamp life but, increase light output. The table below shows an example where a lamp at normal 120VAC line voltage would have a 75 hour life, however, if the line voltage increases to 130 VAC it will only last 28 hours.

Power Line Voltage vs. Light Output and Lamp Life 

Line Voltage
% of Light Output
Lamp Life, Hours
115
87
130
120
100
75 (Rated Life)
125
115
45
130
130
28

Some lamps have a version for use where the power line is consistently higher than 120 volts. If your projector is equipped with a" high/low lamp" switch you can extend your average lamp life by using the "low lamp" position whenever possible. Also, some projectors are equipped with regulated power supplies that deliver the correct voltage to the lamp. This also extends the lamp life.

Lamp Installation

When installing lamps, be sure the lamps are seated completely. The tendency is to stop at the first sign of resistance. Continue to apply force at the base of the lamp until you are sure the lamp is secure.


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If you have compliments, complaints, suggestions, or help with areas not listed above please contact:

Ron Miller
General Manager
ron@replacementlightbulbs.com


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