iMac 27 late 2009: Blank screen after CPU upgrade, what I broke?

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iMac Intel 27" EMC 2309 and 2374

iMac Intel 27 "EMC 2309 (Finales de 2009, Core 2 Duo 3.06 o 3.33 GHz) ID iMac10,1, EMC 2374 (Finales de 2009, Core i5 2.66 GHz o Core i7 2.8 GHz) ID iMac11,1

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Tony @tonyh2

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Publicado: 9 de mar. de 2022

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iMac 27 late 2009: Blank screen after CPU upgrade, what I broke?

I have upgraded the CPU on my iMac 2009. Now the screen stays blank after powering on, but the iMac is still accessible via Screen Sharing (vnc) and remote login (ssh). I can see that the new CPU is working as expected.

I’m afraid that I broke the video connector to the LCD when I opened and lifted the LCD. Is it possible to test if the faulty part is the connector?

I considered to test the video output via Thunderbolt, but I only have an old monitor with VGA input.

Thanks in advance for any hint.

Added some photos

I bought a cheap Thunderbolt to VGA adapter to test; when I login via Screen Sharing, the external monitor shows a copy of the main screen. So it looks like the fault is somewhere between the connector on the logic board and the LCD panel?

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Can you post a few pics so we can see the connector and the cable end Agregar imágenes a una pregunta existente

9 de mar. de 2022 - de Dan

@tonyh2 - As I had feared the logic board connector needs to be replaced.

11 de mar. de 2022 - de Dan

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Dan @danj

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Publicado: 10 de mar. de 2022

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It looks like the connector was pulled away from the logic board as it looks like its at a bit of an angle and the grounding tabs look like they’ve been soldered down at this angle.

At this point I think you’ll need to replace the connector, using solder wick clean off as much solder as you can from the contacts and then use a hot air station to heat up from one end lifting the connector legs making sure not to damage the pad below. As you unsolder the leg lift it up so it doesn’t resolder on. walk down the connector and then do the ends again being careful not to damage the pad under it. Clean off and tin the pads and mount the replacement connector LVDS Cable Connector (30-pin)

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thank you for your hint, much appreciated.

I think I am not up to this task; I can solder simple things but this connector seems very fine and I have no idea how to solder it, or which equipments I need for this task. Perhaps I should bring it to a repair shop.

But before doing it, can I at least some how test and verify that the connector is the culprit? For example if an external monitor connected to the Thunderbolt port works then can I conclude that it’s almost certain that the connector or cable is faulty?

10 de mar. de 2022 - de Tony

@tonyh2 - The better way would be to check things using The Ins And Outs Of Your IMac’s Target Display Mode

Thats how I would proceed here to make sure the rest of the system was OK

10 de mar. de 2022 - de Dan

I can login to the iMac from another iMac with Screen Sharing; does it mean that the graphic card is working?

11 de mar. de 2022 - de Tony

@tonyh2 - No! That only proves the main logic board is working. What you are accessing is the RAM image in main memory.

You could still have a GPU issue, display or the cables & connectors to the display.

If you don't see a glow in a larked room it also could be a bad backlight LED driver unit and/or its cabling.

11 de mar. de 2022 - de Dan

I can see a glow when the room is completely dark.

Now I should turn on the iMac, press Cmd-F2 to enter Target Display Mode and try to use it as an external monitor for another computer? I think the probability it works is rather low; however when it works what could be the conclusion from it?

11 de mar. de 2022 - de Tony

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Can you post a few pics so we can see the connector and the cable end Agregar imágenes a una pregunta existente — Dan
@tonyh2 - As I had feared the logic board connector needs to be replaced. — Dan
thank you for your hint, much appreciated.

I think I am not up to this task; I can solder simple things but this connector seems very fine and I have no idea how to solder it, or which equipments I need for this task. Perhaps I should bring it to a repair shop.

But before doing it, can I at least some how test and verify that the connector is the culprit? For example if an external monitor connected to the Thunderbolt port works then can I conclude that it’s almost certain that the connector or cable is faulty? — Tony
@tonyh2 - The better way would be to check things using The Ins And Outs Of Your IMac’s Target Display Mode

Thats how I would proceed here to make sure the rest of the system was OK — Dan
I can login to the iMac from another iMac with Screen Sharing; does it mean that the graphic card is working? — Tony
@tonyh2 - No! That only proves the main logic board is working. What you are accessing is the RAM image in main memory.

You could still have a GPU issue, display or the cables & connectors to the display.

If you don't see a glow in a larked room it also could be a bad backlight LED driver unit and/or its cabling. — Dan
I can see a glow when the room is completely dark.

Now I should turn on the iMac, press Cmd-F2 to enter Target Display Mode and try to use it as an external monitor for another computer? I think the probability it works is rather low; however when it works what could be the conclusion from it? — Tony

Synthax @synthax Rep: 37 4 · Answer 1 · 2022-03-11T02:27:49-07:00

Synthax @synthax

Rep: 37

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Publicado: 11 de mar. de 2022

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If you’re not able to solder on a new connector, you’ll need a new logic board. They can luckily be had quite cheaply on eBay.

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iMac Intel 27" EMC 2309 and 2374

iMac 27 late 2009: Blank screen after CPU upgrade, what I broke?

Update (03/10/2022)

Update (03/11/2022)

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