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I have iMac 27 late 2013 in startup i can hear the start sound and the system is working but black screen, usually when unplugged from electricity and left for few hours it comes back to itself. but now even this is not working . start/ off button is working any ideas ?
Not good ;-{ Either the power supply or the logic board or both could have a problem! Often when I see this type of issue the system had encountered a power surge either from the power line or a lightning storm. I would recommend taking your system into an Apple Store and letting them deal with this. The cost will be lower than what you’ll end up paying trying just to get the parts. I would strongly recommend you get a qualified electrician to check your house wiring. Make sure you have a dedicated outlet (or one that is only supporting lights in addition). Make sure the outlet is properly grounded (three prong) and the breaker panel is likewise properly grounded and the grounding point is likewise in good shape. Even after checking out the AC power wiring we’re still not done! You need to get a good surge suppressor or better yet get a good UPS unit. If you find your lights flicker (LED lights more so) you really need a backfill UPS, We were burning out power supplies until we went with UPS’s for our desktop systems. Also make sure your peripheral devices are on surge suppressors at least as a lighting strike can sneak into your system from them!
