Frequently asked questions about projector lamps

• How does a projector lamp work?
• Why is a projector lamp so expensive?
• How to replace a projector lamp
• What should I do with my broken projector lamp?
• How do I know if my lamp is broken? Can I measure this?

How does a projector lamp work?

A projector lamp is a high pressure gas-discharge lamp or a metal-halide lamp. They consist of an arc tube with electrodes, an outer bulb, and a base. Projector lamps produce light by making an electric arc in a mixture of gases. In a metal-halide lamp, the compact arc tube contains a high-pressure mixture of argon, mercury, and a variety of metal halides. The mixture of halides will affect the nature of light produced, influencing the correlated colour temperature and intensity (making the light bluer, or redder, for example).

Metal-halide lamps require electrical ballasts to regulate the arc current and deliver the proper voltage to the arc. Like high-pressure mercury vapour lamps, some metal-halide bulbs contain a third electrode to initiate the arc when the lamp is first lit (which generates a slight flicker when the lamp is first turned on). Pulse-start metal-halide lamps don't contain a starting electrode, but they require an ignitor to generate a high-voltage (1–5 kV on cold strike, over 30 kV on hot restrike) pulse to start the arc.

If you want to read more about the technical details of metal-halide lamps please see this Wikipedia page.

Why is a projector lamp so expensive?

Projector lamps are expensive because simply said, projector lamps are expensive to manufacture. This is because projector lamps are made of borosilicate glass and fused quartz. Because quartz is tough to work with and is very hard, special equipment, which is highly expensive, is needed to heat and mold the quartz.

Scarcity of projector lamps drives their price even higher. Manufacturers protect their investment in expensive materials and time by enforcing high quality standards. The highest acceptable failure rate in the projector lamp industry is around 0.4 percent lamp failures per batch.

How to replace a projector lamp

When you buy a projector lamp you buy a complete module. This means a new lamp with a new housing. Usually the lamp replacement procedure is described in your projector's manual. If you don't have it anymore you can try to find it online. Most manufacturers offer the option to download a manual. If you still cannot find the procedure don't worry, replacing a projector lamp is an easy job. Usually you have to turn over your projector, unscrew some screws so that you have access to the lamp compartment. You can now see the lamp itself. This is also held in place via some screws and possibly you also have to detach the power cable of the lamp. You can then gently take out the lamp. In reverse order you can install the new lamp. When replacing a lamp, please take care not to touch the glass of the lamp.

What should I do with my broken projector lamp?

You should not throw away old projector lamps! They contain mercury (Hg), a toxic metal, and must be properly disposed of or recycled. Please contact us if you wish us to recycle your projector lamp properly. If you send the lamp as a complete unit we might even be able to install a new bulb for you and ship it back to you. Just make sure you contact us first so we can give you the details.

How do I know if my lamp is broken? Can I measure this?

Unfortunately it's hard to say if a projector lamp has failed, unless of course, it has exploded. But, there are a few things that you can check yourself. When the projected image has become less and less it's a sign the projector lamp has reached the end of its life. When the light output is very low or when there is no image projected at all, you can take out the projector lamp and examine it while looking at it from the front. In the center of the lamp you will see a glass part, the strike stem or burner that contains two electrodes. When the burner is not aligned in the center of the lamp anymore it has failed. When you see white or black spots on the burner it has most likely also failed. If you are unsure you are always welcome to take some pictures of the lamp (and the burner especially) so we can take a look for you. Please also read our tips on identifying an expired projector lamp module.

Some people will try to measure a failed lamp to see if any current can travel through it. This is not possible. A projector lamp has no closed circuit as it has two electrodes inside a vacuum. Therefore it is impossible to measure a current.

The strike stem is misaligned and has white spots. If the stem is not clear it's a sign of lamp failure.