What happens if you yank the ROMs altogether? Does that result in nothing at all? If you have an alternate and compatible known working power supply, then try it, otherwise messing with that might be too risky a gamble. It might be worth searching for the power supply's spec'd output and using a multimeter (if you have one, if you don't they're not terrible expensive -- maybe $15-20 for a decent one) to check that the proper voltages are supplied.
Are the ROM ICs pins or the socket pins dirty or anything like that? If there are test points, little plated drilled holes along a pcb trace, you could test continuity of the traces that lead to the socket (check at the solder points of the socket and inside the socket where the IC pins go). You might also want to examine and check the video circuits of the board for the sake of thoroughness. I don't know a whole lot about this stuff, but that looks like a definitely designed test pattern. Although there might be some sync issues, if anyone who knows more wants to comment feel free. The pattern doesn't look perfectly straight and clear to me.
As for the CPU, I think that the fact that it beeps and shows video when the CPU is in means that it (the CPU) is most likely working. If you have a spare working one, it might be worth a test. Best of luck with your troubleshooting.
Are the ROM ICs pins or the socket pins dirty or anything like that? If there are test points, little plated drilled holes along a pcb trace, you could test continuity of the traces that lead to the socket (check at the solder points of the socket and inside the socket where the IC pins go). You might also want to examine and check the video circuits of the board for the sake of thoroughness. I don't know a whole lot about this stuff, but that looks like a definitely designed test pattern. Although there might be some sync issues, if anyone who knows more wants to comment feel free. The pattern doesn't look perfectly straight and clear to me.
As for the CPU, I think that the fact that it beeps and shows video when the CPU is in means that it (the CPU) is most likely working. If you have a spare working one, it might be worth a test. Best of luck with your troubleshooting.