Chosen Solution
After replace power supply, green light back on but still not power up I did replace power supply and logic board and everything looks ok, but cannot start up my imac Update (03/04/2022)
The green light on like that, I will try one by one test, thanks man
Did you forget to plug in the power switch connection?
You can also short across the contacts on the logic board to emulate the switch (just takes a moment)
