Replacing a bulb is easy when the original package is available. It becomes more difficult when the lamp is unlabelled, discontinued or used in specialised equipment. Two lamps can look almost identical while having different voltages, bases, dimensions or electrical requirements. Choosing by appearance alone can therefore result in poor performance, damage or a bulb that simply does not fit.
The safest approach is to treat identification as a short investigation. Gather the information below before purchasing a replacement or contacting a lighting specialist.
Start with the complete lamp
Remove the lamp only after the power has been switched off and it has cooled. Do not force it from the socket. Some lamps unscrew, some twist and lock, some pull straight out, and others are retained by clips. If the removal method is unclear, consult the fixture instructions or a qualified technician.
Keep the original lamp intact whenever possible. The complete lamp gives a specialist more information than a photograph of the glass alone. Its base, pins, contacts, proportions and printed codes may all be needed.
Record every printed marking
Examine the glass, plastic housing, ceramic section and metal base. Write down or photograph all visible information, including:
- Manufacturer or brand
- Model or order code
- Wattage, such as 9W or 50W
- Voltage, such as 12V, 120V or 220–240V
- Lumen output
- Colour temperature, such as 3000K or 5000K
- Beam angle
- Dimmable or non-dimmable markings
- Any letters and numbers that appear to identify the lamp family
Do not discard a code because it appears unimportant. A short combination of letters and numbers may identify the lamp shape, base, wattage, colour or manufacturer series.
Identify the general shape
Common families include A-shaped household lamps, globes, candles, reflectors, PAR lamps, MR lamps, capsules and linear tubes. The shape narrows the search, but it does not determine compatibility. For example, a PAR30 lamp may be sold with different bases, technologies, voltages, beam angles and wattages.
Measure the widest diameter and the overall length, including the base. For tubes, record the full length and tube diameter. For reflector lamps, note whether the neck is short or long. Small differences matter when a fixture has limited clearance.
Examine the base carefully
Look at how the lamp connects to the socket. Screw bases are commonly identified with an “E” code. Pin and twist-lock bases use codes such as G, GU or GX. Bayonet bases usually begin with “B.” The number often relates to a physical measurement, but it should not be guessed from a photograph.
Count the pins or contacts, measure the spacing where possible and note whether the pins are straight, looped, offset or different sizes. A G4 and G9 capsule, for example, may serve similar-looking fixtures but their bases are not interchangeable.
Check the fixture—not only the bulb
The fixture label may provide the most reliable information. Look for the permitted lamp type, maximum wattage, voltage, base, insulation or enclosure rating and any ballast, transformer or driver requirements. Photograph the label clearly.
For fluorescent, HID and some LED systems, the control gear is part of the compatibility decision. A lamp may physically fit while being electrically unsuitable for the installed ballast or driver.
Take useful photographs
Provide several clear images on a plain background:
- The entire lamp from the side
- A close-up of the base or pins
- All printed markings
- The empty socket
- The fixture label
- The lamp beside a ruler for scale
Avoid holding a tiny lamp far from the camera or photographing it while it is still glowing. Sharp, well-lit close-ups are much more useful.
Confirm the application
Explain where and how the lamp is used. A specialist may need to know whether it operates indoors or outdoors, inside an enclosed fixture, on a dimmer, with a transformer, in emergency equipment or in specialised medical, projection or scientific equipment.
The goal is not merely to find a bulb that fits. It is to find the correct lamp for the fixture, electrical system and required lighting performance. When the markings are missing or the application is specialised, bring the original lamp to Bulb World Lighting or submit clear photographs with the fixture details. Our team can help narrow the options before a replacement is installed.