Model A1174 with 2 GHz Core Duo or Model A1207 with 2.16 or 2.33 GHz Core 2 Duo

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NO Video, NO backlight, everything else fine

2006 model A1174, 20" iMac (first Intel).

My machine is in complete darkness. I believe the screen replacement might have been botched.

Everything works perfect when hooked up to another monitor (mini-DVI -> DVI converter, DVI cable to monitor). So, it appears the GPU is fine.

I see a couple possible culprits:

1. Bad LCD ribbon cable - perhaps if this was totally inop the display would never kick on?

2. Bad inverter - here, the backlight would not come on, which is TRUE however I ALSO do not have an image on the screen via the "flashlight" method.

3. Bad mainboard - something on the mainboard is busted in between the GPU and display cable, but not in the line of the rear mini-DVI port.

If I had lost backlight OR video, then this would be a piece of cake, or at least manageable.

Perhaps, #4 could be that TWO parts have failed, perhaps #1 and #2. But that sounds a bit unlikely... but I could see how that *could* happen (say, inverter dies, new screen installed by "mistake", ruins lcd ribbon in the process?)

I'm afraid I might just have to "shotgun"-select parts until something works...

:::::POST-REPAIR EDIT/NOTE:::::

Read the comments below.

I had a panel with revision number/code (or type code???) that corresponded to an older 20" G5 iMac. EVEN THOUGH the main MODEL NUMBER was IDENTICAL, apparently the panel was NOT compatible. Upon purchasing the correct panel, the iMac was fully functional. Again, the details are below!

Short version: order the EXACT PANEL!

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Alec J, just to verify, you did replace the LCD? Why? What happened to the old display? Have you tried the old display to see what happens. Yes, looks like your GPU is okay:)

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Alec J, check the diagnostic LED's first and let us know what you find. "Diagnostic LEDs

The iMac (20-inch Late 2006) has three built-in diagnostic LEDs and a front power-on/sleep LED on the main logic board that can help you to troubleshoot the computer.

To Access the Diagnostic LEDs:

1. Follow the take apart instructions to remove the RAM access door, front bezel, and lower EMI shield.

2. Locate the SO-DIMM slot and LVDS video connector. The three diagnostic LEDs 1, 2, and 3 are located below the battery and to the right of the memory slot. Note that the LEDs are marked 1, 2, 3. An additional front bezel LED is located in an opening at the center of the right speaker,

LED #1

• Indicates that the trickle voltage from the power supply has been detected by the main logic board. This LED will remain ON whenever the iMac is connected to a working AC power source. The LED will remain on even when the computer has been shut down or put to sleep. The LED will turn off only if the AC power source is disconnected or the power supply is faulty.

LED #2

• Indicates that the main logic board has detected proper power from the power supply when the computer is turned on. This LED will be ON when the computer is turned on and the power supply is working correctly

LED #3

• Indicates that the computer and the LCD display are communicating. This LED will be ON when the computer is turned on and video signal is being generated.

Front LED

• Indicates that the computer has power but no video signal (e.g., the computer is starting up or the display has entered Sleep mode, turning off the video signal). This LED will pulse when the entire system has entered Energy Saver mode." You do have fuses on your board that you may need to check, but lets find out which logic board you have. If you can give us the 830-XXXXX number of your logic board. If not, give us the last three digits of your serial number. That will help us to properly identify your computer. Hope this helps, good luck.

Fuse Location

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Well, I'm a little confused.

Perhaps we have a mix-up in models? I am unable to find such LEDs in the spot as directed (when I heard about such thing yesterday, I looked for some lights on the board but saw nothing).

It's very possible I mislabeled this thread?

My board number is 820-1888-A.

I can't seem to find the EMC number to clarify... I figured it would be on the bottom of the foot, where the A1174 is found, but... I don't see it. Heck, I can't find the serial number. I'm going to take a wild guess and say that was on a sticker, which isn't to be found. Crap?

Back to the LEDs, I'm assuming they are those tiny surface-mount ones, that sorta look like the other tiny capacitors and resistors that are all over the board except sorta translucent. Right?

Anyway, here's a picture of that area.

http://i57.tinypic.com/4t7r84.jpg

board is stamped with a (c) 2005 right under the aforementioned board number.

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Ooh, here's another tidbit. When I power it on with the external monitor, THAT is when I can see my nice grey screen (no OS at the moment) with "?" folder icon.

When I power it on WITHOUT the external monitor plugged, the FRONT LED (the one that flashes when in sleep) is lit, solid/full, and if I plug in the external monitor now (after it has booted without), it does nothing else.

Also, it does have the startup "bong!" regardless of setup.

I'm really hoping for a fuse or something... which I can replace, even if surface mount. I just couldn't begin to accurately diagnose it. I see there's a fuse right near the LVDS cable, but it appears to be one of those "resettable" fuses like the ones Littlefuse supplies. It is marked with a "50" (preceded by some W looking symbol).

I appreciate your help! I think we can figure this one out!

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Alec J, post an image of your board with your question. Point out the component you are referring to, I am sure I can either verify or invalidate the component as a fuse:-) Use this guide to add images to your question. It will allow us to see what you see.

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Here's the full board:

http://i62.tinypic.com/2zibm9x.jpg

And here's what I am assuming is a fuse of some sort (green square):

http://i61.tinypic.com/t7mtdt.png

Marked, I belive, F9710. Wild guess that it is near the LVDS cable plug...

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that is F9710 fuse 0.5AMP-13.2V and it is used for the DVI interface. there are four more fuses that you can check. F4600 FUSE_SM-LF

F4601 FUSE_SM-LF

F4602 FUSE_MINISMD-LF

F4701 FUSE_MINISMD-LF . Check those for continuity.

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