No power. No LEDS with display removed?

My IMAC went dead while using it. No screen, no fans, nothing. I unplugged it and and plugged it back in. When I turned it on I heard something which sounded like a component failing. My background is in marine electronics and use to doing component level repair. My first thought was a power supply. I used the guid here to remove the power supply. I did not see any thing that looked like it failed. No swelled caps or burn areas. I put the supply back in and checked the 120 volt to the board, it was there. Not having the pin outs to the board I couldn't check other pins. Reading more about this IMAC I saw the questions on the LEDs. I have no LEDS turning on.

Does the display have to be in place for the LEDS to work?

Are there schematics for the power supply?

Are there interconect schematics for this IMAC?

I still think it may be the power supply but would like to do more testing before I order one.

Thanks for any help