2020 27 in IMac will not turn on.

[MacManager123]

I have a 2020 27 inch iMac on my hands that won't power on. When the power button is pressed, the psu makes a high pitch hissing sound and the display backlight turns on for a second before it shuts down. I initially though it was the psu but but the problem still persists after buying a used psu and installing it. All of the debug lights on the logic board turn on so I really have no idea other than a possible gpu failure. It is a 5500 xt I believe and have heard about issues with that gpu. Logic boards sell for over 500$ so would really like to find a solution. Any help is appreciated!

 

[Sully]

Go to one of the AI’s and paste your question. I used Gemini. I won’t post the the answer because there’s a lot of hate for AI. And I get it, hallucinations are a thing. But, it spit out a lot of ideas that might be helpful to you.

 

[MacManager123]

Gemini thinks the issue is gpu related, I'll work on it more tomorrow.

 

[MacManager123]

I've done some more research and I'm starting to think that the used psu I bought is broken. Don't know if I should order another. Any ideas?

 

[TwoH]

Interesting the issue persists with a swapped power supply - as it does sound related to the issue from what you've described.

Have you tried doing a DFU? 2020 can be DFU restored.

 

[MacManager123]

Interesting the issue persists with a swapped power supply - as it does sound related to the issue from what you've described.

Have you tried doing a DFU? 2020 can be DFU restored.

The PSU I bought was only 10$ (15$ shipping) which is really cheap so It's very possible that both PSUs have the same issue. Is there a way to test them with a mutimeter? I have not tried a DFU yet but will do so when I have the chance. The Imac died while asleep, not while under load so I don't see how it could be the logic board. On the other hand, I have had some slight graphical glitches with it in the past. I'll try a few other things and a DFU soon and give an update back here.

 

[TwoH]

Is there a way to test them with a mutimeter?

DC voltage on multi meter and check that it is giving 12 volts from the output into the logic board