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A1418 / EMC 2833 / Late 2015 / 3.1 GHz Core i5 or 3.3GHz Core i7 Processor. Released October 13, 2015.

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Power Issues; Troubleshooting Power Board

Hello all. I've acquired an EMC 2833 iMac, and I'm having problems with the power board. When I pulled the unit apart, the wires from the power button were loose; I suspect that when they came loose, they shorted something on the power board. Right now when I plug the unit in, LED1 flashes briefly and goes dead. Plugging the power supply in with no load, I'm able to find the 12V line, but I'm not sure where everything else is supposed to be.

I'm capable of doing component level repairs, so I'm hoping I can narrow down to a specific component that I can replace, but I either need a pinout for this power supply, or at least a list of values to expect at specific places to try and narrow down what part is bad.

Thank you in advance.

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Not sure how the power button would short out the power supply here. The button is a simple momentary blister switch and the connection is well protected. One side is ground and the other leg when shorted to ground triggers the soft switch logic within the power supply. Refer to Step 32 in this guide iMac Intel 21.5" Retina 4K Display Logic Board Replacement. Shorting the header should allow the system to start are you able to get to that point?

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First thing I tried was shorting the legs on the connector for the switch. Nothing happened when connected to the main board, but when disconnected, I was able to read 12V on the larger connector to the main board.

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@skyla93586 - So, the power-supply is working then, then you'll need to grab the schematics and board view drawings to trace out the rest of the power rails on the main logic board.

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@danj where can I find those?

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@skyla93586 - within the copper foil layer you should find a board number 820-???? Once you have that Google that I'm sure you'll find a set available.

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@danj I've got the mobo out, but I'm not sure what you mean by copper layer?

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