In our box room there are 4 ceiling halogen spotlights/downlights and a dimmer switch. A couple of weeks ago my son switched them on and tripped the electrics. I assumed one of the bulbs(50w) had blown. When we switched the electric back on none of the bulbs lit. I only had 1 spare so i put it in thinking it could be possible he blew all 4 bulbs but even that 1 new one doesn't light. Checked wiring in dimmer and is fine. Why would they all go off???