Vintage Synth Repair

I am in desperate need of some direction! I picked up a broken ARP Omni MK1 last year on craigslist as a project, because of the success I had read about online of people bringing them back from the grave.

There is no sound at all coming from this synth! I am a DIY hobbyist, but not much of a schematic jockey, so I have tried to restore and overhaul the Omni. The lights light up and the switches turn the lights on and off. The power supply is spitting out -15 and +15 like it should, just no output from the main out, synthesizer out, or any other out.

You guys are going to laugh.

I replaced the following:
-All tantalum caps, decoupling and envelope
-All CD4XXX ICs, on every board (yes, I have WAY too much time)
-LM1458s on string control board
-LM301 on filter board

Now I am at an impasse. I really want this thing working with a passion, and getting rid of it this far in the game would be a big mistake. Is there any part of the synth I should be looking at? I have an oscilloscope, should I be probing a certain place? I've worked on smaller, less complicated synths in the past, but the Omni is damn near confusing.

One last question: The phaser board connector was upside down when I received it. Is there anything that could fail on the phaser board that would cause it not to make any sound?

I truly appreciate your help, thank you so much for your time!!!