Check the reset signal on pin 40 at the 6502 CPU. If it is Low (0V) reset is active and the board won't start. If it is High (5V) check if the clock signals are present. They should be there at pins 37 and 39 at the 6502 CPU and pin 39 at the 6532 RIOT's. Use a logic probe or better oscilloscope to check. If these are all ok a testrom is a nice attribute to test your CPU board. Another possibilty is to send out your board for repair to someone with decent knowledge and experience like Chris Hibbler for example.