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

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Verifying bad logic board vs GPU

UPDATE: I have replaced the motherboard. I have replaced the power supply. Neither of these have solved anything.mi have the exact same symptoms. I guess now I don't get startup noises, but I assume that's because of moving ram around and such. But perhaps it's important.

As a recap: screen and USB controls failed at the exact same time. No keyboard commands forwarded through USB. No wireless mouse connection. indicator lights 1, 2, and 3 come on on power up, computer boots, fans run, but no screen, no USB command

I have an unformated SSD that I tried plugging in as a replacement of my HD with no additional response from either.

Since it is neither the power supply or the logic board, what is the next step?

Thanks again all

Original post:

Early 2008 iMac 3.06GHz. Has worked flawlessly up until 2 days ago, when screen went to black while in use.

Upon restart, boot chimes start, have noise from fans and disc tray (with a disc I need to get out of there), but no screen (stays black). Wireless mouse does not seem to be connecting to anything.

Attempt NVRAM reset. Press Command + Option + P + R after boot noise, nothing happens. Discover USB ports no longer sending/receiving power or signal.

Would love to keep as much stuff out of the landfill as possible, so thinking about fixing and upgrading to SSD while everything is opened up. El Capitan really made the computer feel good again, I can only imagine an SSD enhancing that.

Thanks everyone

Answered! View the answer I have this problem too

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OK, I've been watching you and Dan dance around here and there are to many toes being stepped on. It's obvious to me that you two can't dance.

Shine a flashlight on the screen at an angle, when it is booted and see if you can discern the desktop. If so, replace the inverter. Here's how: iMac Intel 20" EMC 2133 and 2210 Inverter Replacement

I know this is the guide for the 20", doesn't seem to be one for the 24", but it will work. Here's the Manufacturer Part Number : 661-4184. Here's where you can get one: http://www.macpalace.com/661-4184-invert...

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I did try the flashlight thing, and I got no discernible desktop. I will verify again when I get home. I'm just not sure why I would get no response from a keyboard plugged into the USB if it's strictly LCD related issue.

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Try different USB ports and different keyboard. Try plugging just the mouse in. It can be tough to solve with multiple issues, so see if you can solve one first.

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I tried a second keyboard, tried different USB ports. I'll try a wired mouse as well. But second keyboard/different ports didn't do the trick.

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Screen shows nothing. Not even a flicker, no image seen with flashlight. Wired mouse shows no signs of life. Mouse has LED indicator lights, did not turn on. Tried to eject disc by hold left mouse button, nothing.

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Can you possibly switch to a wireless keyboard?

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Sounds like your power supply went Vs logic board or GPU. If your USB ports lost power.

You could try connecting the system up via a FireWire cable to a second Mac using Target Mode. If you can get the internal HD to show up you then know the power supply is OK.

Update (12/31/2015)

The first test was non invasive. Luckily Apple offers a set of diagnostic LED on the logic board. Are you up to opening your system to check things out? If you are here is the IFIXIT guide on the diagnostic LED's: Technique: iMac Intel 24" EMC 2134 and 2211 Diagnostic LED's. Let us know what you see. Good Luck!

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Yeah, I've been trying to rule out PSU as well. It just seems odd that it would both stop sending picture AND the USB's go out, but still get startup sounds.

I have an appointment set up at the apple store tomorrow. It sounds like my computer is old enough they might not look at it, but do you think they would take the time/ have the ability to do the firewire thing you suggest to verify? Honestly don't have too much experience with the genius bar.

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Also, if it makes a difference, I borrowed a keyboard with indicator lights to confirm that it wasn't maintaining any signal. The indicator lights flashed at the very start of bootup, but they did not stay on. Would that change your diagnosis?

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What are the diagnostic lights telling you?

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Alright., lights 1 2 and 3 on with system on. Lack of Light 4 would indicate Issue sending video to LCD. What might this mean in conjunction with USB's failure?

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Then your logic board is bad.

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