Chosen Solution
From what I read, I’d guess that PSU for iMac 27” 2009/2010/2011 were the same. It’s not clear if 24” PSU would be different (I’d it would be stupid from Apple to have different PSU for different iMacs, but…). Is there any list of PSU compatibility out there? It’s a bit frustrating to wait for exactly you iMac to appear on the “sold as broken” list.
Yes the 27” iMac PSU, 310W is the same for 2009/10/11 systems. Just like the 21.5” iMac PSU, 205W is the same across the 2009/10/11 systems. The older 2009 20" PSU, 180W and 24" PSU, 250W are different! And the 2007/08 systems are yet different again! 2008 20" PSU, 180W & 2007 20" PSU, 180W are each different from each other (wiring difference) yet the 24" PSU, 250W works for both 2007 & 2008. As for why these are different mostly its Wattage as Intel altered the power requirement for the chips over time. The newer Thin Series from 2012 onward are also a bit different! The Late 2012/Early 2013 21.5" PSU 185W is different from Late 2013/14/15 21.5" PSU 185W and the 2017/19 21.5" PSU 185W is different again! In all three cases the mechanicals are different. The Late 2012 27” PSU, 300W, is different from the 2013/14 & Mid 2015, and the Late 2015/17 is different again and lastly the 2019/20 is also different! Apple kept moving things about mechanically. Not sure why you want a broken PSU?? The ones I’ve listed above with links are from a good supplier which I use based in the UK. iFixit also sells the 27” 2009/10/11 iMac systems iMac Intel 27" EMC 2309, 2374, 2390 or 2429 Power Supply
