Chosen Solution
I bought an old iMac for $50 a week ago and have been trying to figure out since what’s wrong with it. None of the diagnostic LEDs light up when the power is connected to the computer. I have tried two separate power supplies, both of which show the same issue: no pin, when measured relative to ground, shows any output voltage. I followed the voltage chart here, but no pin shows anything on either power supply. +120 VAC is present across the leads coming from the wall, so the board is receiving power. I tested the fuse on both, and on one the resistance indicated it was blown, so I short circuited it. The large 150 uF, 420V capacitor on each board had positive leads that looked heavily corroded, so I soldered a new one onto one of the boards, in case that was the issue. Alas, the issue still remains. Any ideas?
@cloonam it seems like you are dealing with two separate power supplies with a bit of history to it. From what you are describing it does sound like both of those have failed. Without a schematic of the power supply it will be difficult to repair them. Give us the numbers on the board of the PSU should be Delta power supply. I’d try and start with a known-good power supply for your iMac.
