Model A1225 / Mid 2007 and Early 2008 / 2.4, 2.8, or 3.06 GHz Core 2 Duo processor

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My iMac intel won't boot up, probably PSU?

Hi everyone!

I've got a late 2007 iMac intel 2134 that won't power up at all. I confirmed that the AC cord is working, and then checked the LEDs, but none of them are on. At this point I'm fairly sure the problem is the Power Supply Unit. I have currently removed the PSU.

So here's my question: is there any way for me (very little electrical experience) to test the PSU to make sure it's faulty before ordering another $140 part? Also, how can I check the connection between the AC input and the PSU?


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You could use an Ohm meter to test continuity between the blades of the AC outlet on the back thru to the connector on the PSU. I would strongly not try to test this live (AC)!

It sounds like you have isolated this down correctly to the PSU. I would also point out you could have gotten an electrical spike (lightning) which killed it. Make sure you have a good surge suppressor outlet strip and/or a UPS for the system and your accessories are plugged into.

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The plot thickens! I ordered a new PSU, and as I was installing it I made a new discovery. When the PSU is plugged in to everything (the AC input, DC output, and thermal sensor I believe) *except* the LCD screen, the computer boots fine, and all 4 LED diagnostic lights are on.

However, if I plug the LCD screen into the power supply, the computer won't boot at all, and none of the LEDs light up. I know next to nothing about electrical engineering, but does this mean that the LCD is shorting out the rest of the computer?

Thanks again!


Yes, and no. It sounds like it, and it is possible. Check your connector as well....


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