iMac mid-2011, EMC 2428 - Does not power on after power outage
Very reliable system. No problems since its original purchase about 10 years ago. It was on standby last week during a thunderstorm (lots of electrical activity) that led to 3 or 4 brief power outages in a row. After the storm, I noticed that the system wasn't up anymore and that it would not power on. I've tried all the obvious troubleshooting steps, such as holding the power button for 10 seconds (with or without the AC power cord attached), resetting the PRAM using Option Command P R, and resetting SMC. I even swapped out its PSU and used a known-good AC power cord. Nothing has worked. The one relevant observation that I can share is that with the LCD not attached, the system powered on. It played an audible alarm for memory not being present every five seconds, and the fan started quiet, but then ran at full speed. Also, the LEDs on logic board came on all green. Once I plugged the LCD (and other cables) back in, the system would not power on again. No chime; no fan; just a black screen. One other relevant piece of info is that I took advantage of having opened the chassis and replaced the mechanical drive with SSD, and upgraded its RAM to 16 GB. To me, it appears that the LCD has to be replaced, but before I invest more money into an old (but much loved) system, I'd like to hear from some of the resident experts on whether they think the LCD is the culprit. Thanks for your ideas.
iMac 21.5″, macOS 10.13
