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Erick
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Powers on then off immediately, bad PSU?

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Ok I have a imac a1145 that I bought broken, and initially it would turn on randomly and sometimes the fans would speed up to max rpm. So I took out the logic board and noticed 2 6.3v 1500uf bad caps. I replaced them with good ones, but now the imac will turn on for a split second and turn back off. I noticed on the logic board that the #1 green led indicator is on once the power cord is plugged in and #4 red led indicator turns on after I try to start it. I have looked online for what they mean and have gathered that the #1 is tricky voltage (that's vague), and #4 is overheating. Is the #1 indicator specifically for the PSU or does it cover the logic board too? Any ideas or suggestions would be great, I am at my wits end with it and really don't want to start buying unnecessary parts. Thanks for the help.

Edited by: oldturkey03 ( )

Yeah I'm sure, the striped side is negative and the board is clearly labeled with a + sign for positive. The only thing I can think is that I did not replace the caps with the same physical sized caps. One fits standing as it should and the other I laid on its side and ran wires from the legs to the board. I don't see how that would be an issue but maybe I'm wrong. I did have a bit of trouble getting the one that is standing properly to go back in the holes, so maybe I damaged the cap.

Erick,

Ok so I replaced the 2 caps again with known good ones, and now it acts a little better when trying to turn on, whereas before it wouldn't always flash the white led and now it always turns the white led on every time but I still got that #4 indicator light on. Is it possible to have a cold joint on either the GPU or CPU causing this? If so would reflowing them with my hot air work station fix it?

Erick,

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rj713
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Here is a link to a previous post with the guide to what the lights mean. From what you describe I wonder if you don't still have one or more bad caps. Are you certain you installed the new caps with the correct polarity? Good luck

http://www.ifixit.com/Answers/View/77780...

Edited by: rj713 ( )

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