Chosen Solution

The power supply in this iMac A1311 EMC 2308 doesn’t look healthy to me. I know the logic board isn’t working. I get power when I hit the button but just a black screen. Nothing on external display. Is this normal for the capacitors to look like this?

Power supply 1

Power supply 2 Update (12/21/2017) I’m ordering a logic board. I didn’t know they had two variations of the same part: one with graphics slot one integrated. I have good luck and got the integrated (listing didn’t indicate type) so I’ll be getting one with graphics slot soon.

You may want to review the onboard diagnostic LED’s which is very close to the same location as this system: iMac Intel 24" EMC 2134 and 2211 Diagnostic LED’s Jump to Step7. Let us know what LED’s are lit.

The way to test the power supply is to take a multimeter across the DC output, and see what it reads, then compare it to the expected output. If they are within .05 Volts of each other it’s fine.