This is a Sansui 9090 pc board just behind the front panel. We are seeing more and more examples where the display power switching has failed. Some blackout dial type receivers would cut the display lighting when switched to phono or aux. Unfortunately, the ring on the mode switch that handles power can fail. Obviously, no new mode switches are available.
The mode switch is in the upper part of the picture. The small blue wire with a red flag on it bypasses power switching. The trade off is that the dial lighting remains on in all modes.