iMac No power hardware troubleshooting using Diagnostic LEDs - YouTube
SOLVED: iMac wont start, only diagnostic led 1 on - iMac Intel 27" EMC 2309 and 2374 - iFixit
What to do when your iMac won't turn on?
27inch iMac (late 2013) Diagnostic LED 1 flickers then off, already tried a new psu(AliExpress). Any ideas? do I try logic board next? : r/LukeMianiYouTube
iMac Retina 27-inch Late 2012-2015, Mid 2015 Service Guide to Repairing PDF file | eBay
SOLVED: Where are the diagnostic LEDs on the iMac mid-2011 27" EMC 2429? - iMac mid-2011 27" EMC 2429 (2.7GHz i5) - iFixit
led diagnostic iMac 27 pouces 2011 - esimport
iMac not turning on, Service LED#1 blinking - iMac Intel 27" Retina 5k Display - iFixit
SOLVED: Won't Boot: How to diagnose if Logic board or PSU at fault? - iMac Intel 21.5" EMC 2428 - iFixit
SOLVED: Won't Boot: How to diagnose if Logic board or PSU at fault? - iMac Intel 21.5" EMC 2428 - iFixit