Philips powered subwoofer

The power doesn't  come on.  There is a red LED for standby and a green LED for power on.   I took it apart and checked the fuses and they were OK.  When I put it back together it worked for awhile.  I didn't find any loose connections. Could the on off/volume switch be getting hot? It started as an intermittent problem but has gotten worse.  If it is the switch , where could I get a new one?