Posted October 22, 2024 at 10:44 GMT
Remove the lower glass and check the security of the ribbon cables to the lower panel (connector P63), and the ribbon connectors to the left and right side of the panels. Check also all those cables/cnnections that are being disturbed when rotating the Beocenter top panel into the service position.
Do you have a service manual/multimeter? If so, I would start by checking power to those lower panels for which you need to refer to service manual. There is also a Test Mode but this is initiated by short circuiting two pins on the lower panel so it may not work, and I doubt that it would tell you much.
Anything more than that and you are going beyond my knowledge, but let's hope it's just a loose connection!
Location: Warwickshire, UK