Flashing blue light, no audio or video, can't enter safe mode

I had a problem with the unit starting to power on and then immediately shutting down. After some research, I decided that due to a power surge or it being dropped, the GPU needed to be reballed or something. (It was working normally prior to the power surge and subsequent dropping events.) So I decided I could replace the mono and all would be well. I discovered that the mono is paired to the optical drive (according to ifixit) and that they had to be replaced together, so I bought a paired mono and optical drive (making sure that my version number matched the replacement parts) hoping this would be the cure. Upon receiving the parts, I discovered the replacement mono did not match my original after all. There were a few extra capacitors and chips on the new one and PSU connector had 5 pins while my PSU (and original mono had 4). So I tracked down another PSU with 5 pins. Now I've replaced all internal electric components (except the hard drive) and essentially built a"new" ps4. (And spent $200. I saw a new one at target on sale for$300. Should have grabbed that instead) The rebuilt ps4 now apparently powers on but just stays on in a state with the pulsing blue light no audio or video. I can shut it down holding the power button, but cannot get it to enter safe mode. Holding power button from powered down state causes it start up as described and after 12 to 15 seconds of holding the button, it powers down as described.