Chosen Solution
Same old initial problem, black screen and no response, however I have no diagnostic LEDs. General consensus was to replace the PSU and power cable. After doing this I still have no diagnostic LEDs. (I have since returned the newly order PSU) The logic board would be a logical place to move to next. And that brings me here. Is it possible that the PSU has blown the logic board in some way but still show voltage passing through the power cable, PSU and logic board? And if so, upon replacing the logic board, is it possible the old PSU could blow that too? Both old and new PSUs had a very quiet slight electrical hum and this is the only sound the Mac makes when the power cable is plugged in. The model I’m using is the iMac 27" A1419 Late 2015 5K i5 3.3 GHz.
Hi It is very possible that the PSU caused a power surge unfortunately When power supply’s fail they can take lots of things down with them like the logic board and screen… If you can take the logic board out and look for any burn marks or discolouration ,that will help indicate if the logic board will need replaced or repaired Here’s the guide for getting it out iMac Intel 27" Retina 5K Display Logic Board Replacement If you are unsure of any things you can use this guide to upload some photos so we can help you with it Adding images to an existing question Hopefully this helps Any questions please ask Thanks:-)
