Owner says working , then stored indoors for a few months while at uni and now although bar graph functions etc, no sound in the speakers. I tried it and the same. In the bottom of the case a piece of PPE, sheared off in one piece but not the whole encapsulation, from one of the mains SMPS 6 pin combined controller and powerFET devices. A TOP249YN. As that side powers main +rail of the PAs and the unit does not go into protect, I'm assuming that and the other TOP249Y are in working order and some short-term stress blew off the PPE sometime back in its working history. Under x30 you can see a striated part of the die and no sign of burning or sputtering anywhere on either part. Heat with
110 deg C hot air, to expel humidity , then a piece of mica and then a covering of RTV ? or Grind back any awkward bits of the retrieved section and glue back with RTV , only on the outside, or use RTV on the inside , so in contact with the die (after hot-airing that is)Otherwise the PAs seem ok on cold DVM-D testing and at least one failed PbF solder join found, 20 to 100 ohm, on the notorious wobbly union of boards is probably the recent failure mechanism, the music/speech sw seems ok