Fix a touch lamp by following this straight forward guide.
If you are confident with soldering and general electrical work, this CAN be fixed, provided the electronic unit that contains this part is not sealed with a potting compound. They are usually just a 2 part plastic box, that unclips to reveal a small circuit board, with a small chip, and the THYRISTOR on it. The first problem is getting into the base, to take the box apart. These are sometimes riveted on, so you will have to drill out the rivets, and glue the base back on later ( a glue-gun is good for this).
When you locate the module, take care not to break any crimped wires, such as the earth wire, or sensor wire. You may need to spread the sides with a small screwdriver to defeat the plastic clips holding the two halves together. When apart, locate the largest component on the board, with a metal tab with a hole in it. It will most likely be a BT134 or BT136, or a string of numbers with BT134 or BT136 in as part of it, stamped on this part. If it is through-hole, use a solder-sucker (aspirator) to remove the solder from around each leg of the THYRISTOR, and remove it. If it is on an SM (Surface-Mount) board, then it might be a bit trickier, as you will have to melt the solder from each “tab”, and lift it with a sharp knife, until all three transistor legs a clear of the board. It may have the heat-sink tab soldered too, and you may have to apply more heat for that to part.If it is screwed down with a small screw, and a mica insulator, save those bits, in case the screw supplied with the new THYRISTOR is a bit larger than the original. I believe that the majority do not get warm enough to require a heat-sink, and are “free-air” mounted as in the picture. NOTE: some newer touch lamp modules may have an internal soldered-in fuse, so check this is OK with a meter before proceeding. Replace with the same rating if it has blown. MAPLIN have a good range of fuses. Also see additional information below, regarding a fusible resistor in the negative return on the PCB, that can protect the TRIAC and IC (FAQ information below kindly supplied by BW).
EXTRA PICTURES BELOW FROM 2011: To ensure you do not damage the lamp base and stem when drilling out any base cover rivets, invert it and place in a waste bin with bubble-wrap to protect it.Unfortunately, the module pictured below was too badly damaged to repair due to the control IC being damaged by the gate-to-anode short in the TRIAC after the lamp blew (the IC gate was blown when the resistor was burnt - see the black part in the centre of the picture. Luckily I had a spare module to replace it with. The wire colours are often a one-to-one swap over. Ensure all wires are sound, safe (no nicks) and all protected by the plastic module box after repairing. The base can be stuck back with a glue-gun.
Calculating that a 75W lamp at 240 Volts would only dissipate 0.025 Watts. Although counter-intuitive, driving a 75W bulb through a 0.22 Ohm resistor at 240v only dissipates 0.0215 Watts in the resistor! I ordered two types of .22 OHM fusible resistor just in case: armed with this knowledge, Cricklewood electronics sell two low-power 0.22 fusible resistors: Part No.: G0R22 Metal Film Fusible Resistor ¼ Watt. 0.22 ohms (cost 30p) Part No.: J0R22 Metal Film Fusible 5% Resistor ¾ Watt 0.22 ohms (cost 35p)