I've just had a similar issue, 27" 2019 iMac was running normally , came back to black screen and no response. Powered off but now when I tune it on, I get fan spin and disk activity for a few seconds then it turns off and repeats. Opened up to look at diagnostic LEDs and I'm getting #1 OFF, #2 & #3 ON. Bizarre. Changed RAM and swapped PSU no change.
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I've just had a similar issue, 27" 2019 iMac running normally, customer reported that they came back to black screen and no response. Powered off and then wouldn't boot. When tuned on I could hear fan spin and disk activity for a 5-10 seconds then it turns off and repeats. Opened up to look at diagnostic LEDs and I'm getting #1 OFF, #2 & #3 ON. Bizarre. Changed RAM and swapped PSU no change.
I've just had a similar issue, 27" 2019 iMac was running normally , came back to black screen and no response. Powered off but now when I tune it on, I get fan spin and disk activity for a few seconds then it turns off and repeats. Opened up to look at diagnostic LEDs and I'm getting #1 OFF, #2 & #3 ON. Bizarre. Changed RAM and swapped PSU no change.