The front panel is powered from separate winding on the transformer... I would first check if you have AC coming to your front display assembly. After this it's very simple power supply... check fuse if there is any, check rectifier, regulator and so on. It shouldn't be lot of checking.
I have one of those but I've never taken it apart.
So, if I'm correct the power supply is still working you just can't see the settings for the channels?