iMac mid 2011 issues

[xxbeefydjxx]

Hi everyone

I brought an iMac a few months back from a private seller who said that it had intermittent power on issues.

Specifically, you could plug it in, hit the power button and not a sausage of life would come from it, no fans, no nothing.

Now I know this iMac works fully because I am using it to type this message. I got it home and it didn't do it for a good 2 months but it's started acting up again.

Now comes the weird bit.
I have a display port to hdmi adapter, and because the monitor has a sketchy ground the adapter can ground on the iMac case causing it to spark if you rub the connector against the case.

In the event it doesnt turn on, you just ground this adaptor to the iMac and then hit power and boom it comes on no issues.

I have it all to pieces to inspect the power supply, and the board seems to have gotten damp, like it got a sweat (lol)
I cleaned it all out and still an issue. No capacitors or other components seem to have bulged or show any signs of problems. Could it still be a dud!?
There is also a buzzing noise coming from the top left of the machine, Not sure if it's the IPS PSU or the main PSU.....

 

[nambuccaheadsau]

Whatever alas you bought a lemon. Sounds like PS.

 

[DeltaMac]

Unfortunately, electronics failures are often not visible to the eye.
Making everything clean doesn't really help much either (except for your own health and well-being, I suppose)

Most likely - power supply has a cap, or more than one cap failing.
And, I think the reset by "sparking-up" the HDMI adapter is just a fluke that happens to reset the power just enough to enable booting. If you like the "light-show", then use that (though I wouldn't recommend it from a safety standpoint!)
I predict that replacing the iMac's power supply will eliminate that odd grounding problem, too.

The power supply is, in fact, located in the top left area of your 2011 iMac, so the noise may simply be another symptom of a faulty part. (The backlight board is mounted nearer that top left corner, so yes, could be part of the noise)

 

[signuphere]

I have a mid-'11 too. The power button on the back of the case has always been flakey. It often takes several attempts of hitting it just right to fire it up. A few times it was dead, with nothing happening but eventually it worked. I assume it's a mechanical issue.

My USB ports spark too if the plug touches the case at a certain angle! I don't know what that's all about, but so far they have always functioned and yes, when I leave home I shut it off.