Lone in the night

Hi there. Long time. Last summer, I bought a non working ARP Omni. Powered up: no sound but a small glitch. Here is what I've done to fix it. Deep cleaning. Vacuumed first, then I pull all the board off and bath them. Yes, in water with soap and an old tooth brush to gently scrub. Rinced and thorough dried them with common a hair-dryer. Cleaned the Pratt-Reed keyboard. Cleaned the casing. Sanded the wood ends and sprayed some Pledge. Looks nice now. Check the PSU; every thing was OK in this department. At that time, I had no scope. My first guess was a dead output op-amp. Replaced, but still dead. Suspected the 4007 on upper board; replaced it. Still no sound. Got a small digital oscilloscope (116 $ incl shipping and taxes). Upper Voicing Board. Check the output of main osc: OK, outputs of MK50240: Ok. Checked the 4069s and found 2-3 dead gates. Replaced the dead 4069. Ground was shorted to -15V on Upper Voicing Board. Once forced to 0V, could produced some...