It's hard to tell from the pics since I see two different AC power wires in there.
There's the one going to the switcher, powering it.
Just below is the Original Williams power cord.
Where does the round cord that powers the switcher go? Does it have it's own AC plug or is it wired into the Williams wiring at the base of the cabinet?
If it is wired into the original wiring, then I would check the safety switch and see if it's functioning properly. You can "pull" the switch and it will stay in the out position for testing purposes. Also make sure that the power switch is on.

Re-check the connections on the Safety switch and the power switch. If any one of them came loose or fell off, the game will never power up! It is likely that it is wired this way if you are using the original monitor that requires an isolation transformer. Is the switcher plugged into the Williams service outlet?? Is the fuse by the service outlet blown? (Take it out [with the power off] and test it with an ohmmeter.)
Some who install a switcher just bypass all of that. (except the iso tranformer.) If the switcher IS plugged into the service outlet and you want to try temporaily, just take the AC that is wired to the switcher and plug it into an AC outlet and it should power the boardset (monitor wont be on tho) You should get a code of "0" on the ROM board. If you get the 1-3-1 error, you have another set of problems to face.
More pics of the switcher wiring to the AC would help us diagnose your 'No Power' problem.
Good luck!