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Model A1224 / Mid 2007 and Early 2008 / 2, 2.4, or 2.66 GHz Core 2 Duo processor

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No Video on LCD

Hello, I have a A1224/EMC 2133 Core2 Duo 20" iMac that will not produce video on the LCD. I bought this system with a known no video issue with the intent to fix it. I am a computer repair tech with over 15 years of experience, just looking for some second opinions on how to proceed. When I originally purchased the system it would not produce video at all on LCD or external monitor, but the chime could be heard. I replaced the video card with a used x2600 card from eBay. the original card was a 2400XT. Now it outputs external video but no video on LCD. Below are the troubleshooting steps I have performed so far.

-System will produce video to an external monitor and boot to a setup disk

-Resetting PRAM had no effect

-There is no video on LCD at all. Using a flashlight, there is no ghosted image to indicate there is simply a backlight failure

-The backlight does not appear to be turning on

- Diagnostics LEDs 1,2 and 3 light up right away and stay lit up. LED 4 never comes on.

- Voltages on the power harness going into the LCD inverter are Pin1:3.3v, Pin2:0v, Pin3:-.03v, Pin4:12v. I may have the pins listed in the reverse order.

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After replacing the LVDS cable the screen comes on with backlight.

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See if it's the inverter: iMac Intel 20" EMC 2133 and 2210 Inverter Replacement

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Would a faulty inverter cause an image to not be displayed on the LCD? Since the inverter only powers the CCFLs I would expect to still get an image on the LCD that could be seen with a flashlight.

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Can you see a faint desktop. If so replace the inverter.

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No, I see no image in the LCD. I also tried with a flashlight up to the screen, and no image is on the LCD at all.

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Since I'm not getting any image on the LCD panel I decided to order an LVDS cable first. I figure my steps in order of importance are get an image on the LCD, then look into the backlight not lighting up.

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Joe crwdns2934231:0crwdne2934231:0
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