Hi sir;
I saw 2 problems, Not video is coming, only Photo.
1) buttons, you must sure the +24Vdc are arriving to the cut buttons, and test if cut button are ok, or faulty and replace it.
However if everything is o.k , you have problem with the data of the main computer vs keyboard computer.
You must check this;
Check connection plug BR 500 -
CU16
Exchange card BR
Exchange card HR
Exchange card SPE
2)check switch S309 for open, or defective, or dirty or loose wires. , and ajust it, and the same with plastic curve, according to wiring diagram