Hi everyone. I have a multiplus 1600 that has been faultless for 3 years. Its suddenly stopped working. The batteries are fine and fully charged. The fuse on the front hasn't tripped. The big fuse behind the front panel hasn't blown the unit has full DC power going into it but there are no lights on and no power out and no hum from the unit. Anyone have any ideas for what the problem could be and any possible easy fixes?