In times like this you have to get back to basics. Start with the power and work your way to operations.Open up the Beogram into service position. Check the power from the transformer to the rectifier and verify the DC voltages. You have to make sure nothing funny is going on with the power or else the processor won't function. The transformer assembly has a fuse inside it so it is possible that is blown.I also have to ask if you checked the solder joints you re-soldered under magnification. Those Beogram PCBs have a lot of small solder pads and it would be very easy to have a short between a couple without realizing it. Double check your recap work.It would also be good if you can post several detailed pictures of the boards (component and trace sides).
Reading your original post again, since your Beogram opto assembly light illuminates then the transformer fuse must not be blown. Still, check the power supplies especially the +5 VDC to the processor. It sounds like the processor is not functioning now. If you changed the small electrolytic 47uF capacitor inside the processor housing, did you make sure the ground was connected to that correctly? That capacitor is a little tricky to get installed correctly.