It looks like a replacement logic board can be had for as low as $200 (if I remove and re-use my existing CPU and heat sink). Memory had become an issue at 16GB, but after bumping up to 32GB, it's been fine, and that too ought to be adequate for some time still. The processor (3.5GHz quad core i7) is perfectly fine for my needs, and ought to be for at least several years to come-I'm almost never CPU bound. While this unit is a 7 year old design, the actual machine is closer to 5.5years old. Very much appreciate any insights anyone here might have.Īssuming I can confirm that the replacement power supply is, indeed, operating correctly, I will indeed need to decide if it is worth investing in a replacement logic board, but generally, I don't think I agree with your logic. So is there something beside the power supply that would seem likely to explain this failure, whereby the unit doesn't even get to the point of trying to boot? Seems unlikely that the power supply I received is bad and produces exactly the same failure as the original power supply. So seems like the power button isn't the issue. And if I unplug the system from 120V, LED 1 stays lit until I press the power button, which indicates it's triggering discharge of a capacitor (if I understand correctly, that's expected behavior). There's something still happening when the button is depressed for ~10 seconds. The unit spontaneously lost power while in use-don't see how that could be a power button issue. I have not attempted to test for a bad power button, but the symptoms here suggest against that being a problem. (This is how I discovered the click occurs just from plugging the iMac into 120V power.) Plugging in the superdrive I get the same clicking behavior. Pressing the power button, short or long, produces nothing.
Exactly the same symptom I saw previously: LED 1 indicating trickle power lights shortly after plugging the unit in. Anyway, I swapped the power supply, then before reinstalling the left speaker, reconnected the power button, plugged the unit in, and tried booting it. Don't think that's likely to be a problem, the cable still seems to seat ok. Looks fine except that the plastic is broken/missing on one side of the bracket that receives the data ribbon cable. Ordered a replacement power supply from iFixit (used - only thing I could order and have shipped on an expedited basis). (This testing done with the display removed and disconnected.) Figured that confirmed the power supply was the problem. In particular, LED 2, indicating proper operating power to the motherboard never lit, flashed or anything. Pressing the power button, long or short, did not produce any change.
Ordered a kit and opened it myself, found that just LED 1 was lit, indicating trickle power in an off state. Looked online, found info on the four LEDs indicating power supply and motherboard functionality. Long story short, after being strung along and lied to for 8 days, I finally gave up and went back to pick the machine up. No appts available for a week at the local Apple Store, so I took it to Microcenter, listed as an Apple-authorized repair center. Haven't worked on one of these before, and being a critical machine, preferred not to start experimenting. Since it was trivially easy to test, also removed RAM (had added 16 GB or RAM to bring the machine up to 32 GB about a year ago), but unsurprisingly, that made no difference, either. (I subsequently discovered that the same click occurs if the drive is connected, and the iMac is first plugged into a power outlet, so apparently the drive is reacting to power that is present on USB whenever trickle power is present, even with the system off, and the power button depressed for 10 seconds must result in a momentary interruption of that power.) Pressing the power button on the back, either momentarily produced nothing - no chime, no display, no fan - no indication of anything at all, except a USB-connected superdrive would make a clicking noise after the power button was held for 10 seconds or so. For a moment I wondered if I could have moved the cursor into a hot corner that just shut down the display. No noise or anything when it shut down, just the main display, and an external display connected to it, suddenly went black.
I have a Late 2013 iMac 27, which has been trouble-free since I bought it at the very end of 2014, until two weeks ago, when it spontaneously shut off while I was using it, and then could not be restarted. One line summary: imac spontaneously shut off while in use, won't power back up at all, doesn't seem to be the power supply, so what is it likely to be? Hoping somebody here can help with ideas on what might be wrong.
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