I'm having what seems to be this exact same issue post-10.14.1 install/post-NVRAM reset on my 4,1-flashed-to-5,1…Then I decide to do a PRAM, but I only heard chime once, then the unit hung forever. I have to shut it down, since then the unit won't boot again, tried everything, no screen, no chime, fans runs, GPU fan runs too.
- My system was running 10.12.6 (sorry I didn't note the exact previous firmware version, probably whatever the netkas patcher downloaded way back when though).
- Did 10.13.6 firmware + OS upgrade w/ no issues.
- Then did 10.14.1's 140.0.0.0.0 firmware upgrade as prompted, confirmed proper version showing in System Information and my MacVidCards-flashed 7970 GPU showed 5GT/s speeds.
- Did 10.14.1 OS install and signed into user account.
- Noticed Bluetooth was showing as not available (my Magic Keyboard II was working to sign in as it was connected via USB to charge; Magic Trackpad II wasn't connected at all).
- Cleanly shut down, SMC reset via power cord disconnect.
- Reconnected power cord, waited 5+ seconds, pressed power button.
- Held cmd-opt-PR, system chimed then restarted.
- No second chime, no video, system appears "dead"
My USB ports do seem to be getting power as bus-powered 2.5" drive spins up. However wired Apple keyboard & mouse have no caps lock/lights.You have to find what is your problem. A brick will power on everything but just won't progress from there, USB ports get power.
I added more details here rather than bulking up my post but I sure hope somebody can help…