My ps3 turns but nothing comes up on the screen

All of a sudden my ps3 turns on but nothing displays on my AV TV I already did an video reset when I switched from hdmi to AV. the controller doesnt recognize mi ps3 ,and i have to press and hold the ps3 button for at least 7s for it to turn off, when my uncle was using he would left it plugged in and the other day we had a power outtage so I don't know if it got damaged because it was still plugged in when the power came back I had a professional disassembled it all the way down to the motherboard to clean the dust that built up in it for years of use . and I really don't know what to do I searched everywhere but couldn't find any solution on Google is anyone out there who could help me with this ( it would be a miracle)I would really appreciate it ! Thanks in advance!