This page covers table lamps, desk lamps and floor-standing lamps.
We often see table lamps and the like at Restart Parties. Often, these are quite old - maybe the owner has had them for many years and has a personal attachment to them, or maybe they simply took a fancy to them in a second hand shop. Others are relatively new and have just stopped working. Some may have frayed wires and be positively dangerous. Whatever the history there is a good chance they can be given a new lease of life.
- An electrical safety test is highly recommended, including a visual check, both before and after a repair, especially for an older item.
- As with any mains operated item, it's a good idea to have the plug on the bench in front of you before starting to work, so you can be certain you didn't forget to unplug it.
The first and most important task is to inspect the electrics. A frayed lead, cracked plug or cracked or faulty switch must be replaced. Check the fuse with a multimeter on a low resistance range.
If the lamp uses a filament bulb, check this too with a multimeter. A faulty low energy (compact fluorescent or LED) bulb can only be positively identified by substitution.
If the lamp uses a mains voltage bulb (of whatever sort), test continuity between the plug and the bulb holder with a multimeter on a low resistance range. To do this, touch one probe on one of the pins of the plug (but not the big earth pin) and see if you can get a zero reading by touching the other probe on one of the contacts in the bulb holder. The switch may be off. Try it in the other position. Now repeat with the probe on the other pin of the plug. If you can't get a zero reading in either case then there is a break in the wire, or the switch is faulty.
Lamps using a low voltage halogen or LED bulb normally have a transformer or an electronic equivalent in the base. This is harder to test but you should still be able to test for continuity between the plug and the transformer and between the other side of the transformer and the bulb. Check for any signs of overheating, or for a bulging or leaking electrolytic capacitor.
Getting inside a table lamp with a decorative base such as glazed porcelain is sometimes a little tricky. A porcelain base may have a paper and felt bottom to prevent it scratching a polished surface, and you may need to remove this to get inside. Sometimes you may have to unscrew the top. You may have to pull the lead from the plug into the base in order for it not to get impossibly twisted in the process.
The bulb holder may need replacing. This may be plastic or brass, and with or without an integral switch. Other brass fittings such as threaded tubes and nuts to fit them may also need to be replaced. A wide range of such parts is available online, as well as decorative and fabric-covered flex for an authentic restoration of a vintage lamp. Simply search online for "lamp parts" or "lamp fittings".
A brass bulb holder should have a screw terminal for the attachment of an earth wire. It's very important that this is connected as otherwise a fault could be lethal.
Types of bulb
There are 3 kinds of bulb:
- Filament bulbs. These contain a thin wire which glows white hot when a current passes through it. They are very inefficient and have a relatively short life. Standard types can no longer be legally sold.
- Halogen bulbs are a newer type of filament bulb, somewhat more efficient and with a longer life. They contain a halogen gas which helps preserve the life of the filament and so can be run hotter and hence more efficiently. The envelope is made of quartz rather than standard glass to withstand the higher temperature.
- Compact florescent bulbs are basically just a standard florescent tube bent into a compact shape. Both their life and their efficiency are several times greater than a filament bulb. A florescent tube cannot be connected directly to the mains but needs a ballast and a starter, and a compact florescent, instead, has an electronic circuit in its base. They tend to be bulkier than their filament equivalents and so don't always fit an existing lamp. They may take a minute or so to reach full brightness.
- LED bulbs are the newest, most expensive, but also much the most efficient type. In theory, they could be made to convert nearly all the electrical energy into light. They can be made smaller than compact florescents, so are often made in shapes similar to traditional filament bulbs. Consequently, they are more likely to fit an existing lamp or light fitting. Some are now made with the LEDs arranged in "filaments" to resemble a traditional bulb.
All filament bulbs are dimable though they become even more inefficient as they are dimmed. If you want to use a compact florescent or a LED bulb on a dimmer switch you must choose one which is marked as "dimmable".
When replacing a bulb, be sure to check which sort of base it has. Mains bulbs have either a bayonet cap (BC) or Edison Screw (ES). There are different sizes of ES and less often different sizes of BC. It's a good idea to replace an old filament bulb with a much more efficient compact florescent or LED equivalent, which will also run much cooler. However, compact florescents don't always fit an existing bulb holder or shade. If a compact florescent won't fit and you find the LED equivalent too expensive, at least go for a halogen.
Whilst compact fluorescent and LED bulbs have much longer lives than filament bulbs, premature failures are by no means unknown, generally due to poor quality electronic components in the base. You may wish to keep the receipt if you decide to buy a relatively expensive bulb.