Hi My name is Douglas! I have had a lot to do with touch lamps and how to fix them. For starters you must know how a touch switch works! the main component in a touch switch is a electronic componet called a TRIAC this triac is the one problem with most touchlamps
Causes
lamp stays on
lamp wont turn on
lamp wont turn off
In most cases this is the problem but it is not the only problem
althoughit is the most likley
also could be other components such as capasitors or resistors triacs are avaible from any Electronic stores IE Dick smiths Jaycar
common triacs are :BT134 BT136 BT137 uasly rated @ 400-500 volt you can tell if your triac is dead by using a vom on diode test if you get a responce od both sides of the triac NOTE don't have lamp pluged in when testing. Also some touch lamps are not sevesable as they are coated in a plastic block