2010 27” iMac won’t turn on

[Emdoller]

My sons 2010 imac 27” hasn’t been turned on in 5 years. Worked before that. I turned it on today and nothing turned on. I removed the lcd screen to gain visual access to th diagnostic LEDs and saw the number 1 LED was on. I pushed the power button and the number 2 LED blinked and then both 1 and 2 shut off. I removed power and repeated only this time I shorted the power switch on the board and got the same result.

I tried holding the power button for 1 min with and without power cord and no change.

Given that it worked before not using it it for an extended period I’d be surprised if the power supply board went bad but of course it’s possible.

Anything else I should try?

 

[Nguyen Duc Hieu]

My sons 2010 imac 27” hasn’t been turned on in 5 years. Worked before that. I turned it on today and nothing turned on. I removed the lcd screen to gain visual access to th diagnostic LEDs and saw the number 1 LED was on. I pushed the power button and the number 2 LED blinked and then both 1 and 2 shut off. I removed power and repeated only this time I shorted the power switch on the board and got the same result.

I tried holding the power button for 1 min with and without power cord and no change.

Given that it worked before not using it it for an extended period I’d be surprised if the power supply board went bad but of course it’s possible.

Anything else I should try?

The easiest thing you can try is replace the CMOS battery. Normally a dead CMOS batter may cause weird reaction in the iMac logicboard.
If replacing the CMOS battery doesn't help, then you need to closely examine the logicboard to detect corroded spots.
But even when you detect one, it won't help anyhow. Fixing a dead component on the logicboard is way too difficult for a common Mac user.

 

[GMShadow]

Given that it worked before not using it it for an extended period I’d be surprised if the power supply board went bad but of course it’s possible.

Sometimes sitting for extended periods of time is worse than being left on, honestly. When I retired my parents old Dell Dimension in 2012, after seven years of hard use, I left it sitting for three months, went to use it, and it had given up the ghost.