Vahid, just like anything else, each manufacturer has their own circuit board for the CFL's. From what I have read the most common issue are the failure of some of the capacitors on the circuit boards. You might want to take a look [http://www.pavouk.org/hw/lamp/en_index.html|right here.] Plenty of schematics and values of the components. It might just be what you need to see if you can fix the lamps. Of course I am making the assumption you are talking about CFL. Hope this helps, good luck.