I have 5 mains voltage downlights in living room wired to 500W dimmer switch. This is the 3rd time the dimmer has blown, originally i was using 50W bulbs but i then changed them to 35W internally fused bulbs hoping this would prevent problem. bulbs have blown previously and has tripped the mains fuse but dimmer been ok, the dimmer has a fuse inside but the unit is sealed so cant check it. Anyone any ideas on what the problem could be???