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Modelo A1312 / Mediados de 2011 / Procesador Core i5 de 2.7 & 3.1 GHz o Core i7 de 3.4 GHz

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Screen completely black, what could be wrong?

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My 2011 27” iMac got black screen (doesn’t show any sign of power), but images show correctly through thunderbolt port on external monitor. Is this due to the GPU failure or might be something else on the logic board?

Any ideas?

Thanks,

Contesta esta pregunta Yo también tengo este problema

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@oldturkey03 - Yeah, I just noticed that part after Dan suggested to check that area. I don't think I'm capable enough to repair it, most likely I will order a new logic board over eBay, but thanks for your comments though.

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@lovecd yw. If nothing else make sure you do not just throw out the board. It can be repaired. Sell it online or give it away. NO LANDFILL STUFF

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@oldturkey03 - Hi, sent you a message through email, did you receive it? Thanks!

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@oldturkey03 - Just re-sent it, let me know if you got it this time.

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Sadly this sounds like something within the internal display panel or the displays LED backlight driver logic that’s messed up.

Using a flashlight sitting on the display at a sharp angle you should see a faint image of your desktop and its icons. If you do then this is a LED backlight driver issue otherwise its the display assembly and/or the cables which connect it to the logic board.

Review this guide: Reemplazo de la pantalla del iMac Intel 27" EMC 2429 Step 6 shows where the LED backlight driver is located, carefully remove it if the display is showing an image with the flashlight and inspect the back side.

Update (01/13/2022)

Well, your system appears to be mis-wired review these connections:

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The orange marked connection goes to LED driver board

Here’s the V-Sync

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And here’s the display power and signal cables

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Lastly, we have the backlight power

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Update (01/16/2022)

Here’s what I have, I generally don’t disconnect the cables from the display, and when I do its often to replace the data cable.

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Here’s a view of the T-CON board which you can see the connectors. I believe the cable go to the far right connector.

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Update (01/10/2022)

I won't belabor any more on the expected cable connections. I have never seen the setup your system has.

I don't see how the display backlight is powered as the Orange port needs to get to the display to power it. The V-Sync is needed to remove the LED strobe when its not in sync with the LCD's scan rate.

Think of a Stroboscope effect how short bursts of light can make moving object as if they are standing still. If the rate is off (RPM) to the light strobe you will se the movement and it could appear to be going backwards! This is the same idea here so the rate of scan is in sync with the firing of the backlight LED's. So it needs to be connected to the LED Driver board. The signal is coming from the displays T-CON board to the LED Driver.

We the SATA port wiring is also a mess! The original setup was this when Apple sold the system with a HDD:

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The few systems Apple sold with a 256 GB were wired differently! Here the SSD is mounted underneath the logic board!

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So either someone took the SSD out or to get around the HD thermal sensor they thought they could cheat! The problem is if you put in a HDD it can run much hotter than a SSD! So its like driving a car on the interstate without any oil in the engine and not being the wiser as the low oil and temp gages are disconnected! Sure for the first 50 miles you may get down the road, but… there will be a point the engine will seize up.

So what is the problem solution? You need the HDD thermal sensor if you have a HDD in the HD bay. Apple had a custom HDD but for them so the manufacturing thermal sensor within the HDD was accessible to the systems SMC logic. What you need to do here is put in the iMac Intel 21.5" and 27" (Mid 2011) SSD Temperature Sensor if you are plugging in a 3rd party HDD. If you are putting in a SSD instead then we can get away using the Apple SSD setup.

Now let’s make one important point! If you are doing ay heavy processing or graphics you really should install the thermal sensor so SMC gets a better idea on what happening. To add to this you really need the low oil and oil temp to know whats happening! That means you need this! TG Pro it given you the needed gaging to see whats happening! And also can help you push the fans when things are getting on the warm side.

Well I gave you the back of the T-CON board for reference. Without pulling off the metal plate to locate the V-Sync port I can’t offer anything more.

Imagen de iMac Intel 21.5" and 27" (Mid 2011) SSD Temperature Sensor

Producto

iMac Intel 21.5" and 27" (Mid 2011) SSD Temperature Sensor

$39.99

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27 comentarios:

@danj - Hi Dan, thanks for your message, I didn't see any faint image at all, it is just completely black. However, when I remove the screen assembly, I found there is no vertical sync cable on the display, and there is a cable connecting between where the vertical sync port on the board (the one next to PSU) and logic board. So, there are only 3 wires on the screen display (LED backlight driver cable, display data cable and display power cable), is this supposed like that or there are two versions available for 2011 iMac 27", and mine just falling into the second version? Any ideas?

Thanks,

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@lovecd - sounds like someone mis-wired things.

I only know of the one Apple design at least mine is setup with all of the cables as outlined in the guide and the systems I had serviced many years ago now all had the same setup.

Take some pics so I can see what you have Agregar imágenes a una pregunta existente

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@danj Hi Dan, just added some pictures, any ideas what should I do next?

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@danj Hi Dan, thanks for the diagram. A question though, the one you marked orange, where should the other end of this wire connected with, on back of the display screen? And I didn't find that v-sync cable wire from the display itself, not sure if this wire is necessary or can be ignored. Any ideas?

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@lovecd - Check the display under the covers you must have a missing cable.

I don't like to ignore parts that clearly belong. Someone may have fitted the wrong display on the system which is the other possibility.

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@lovecd - Well, I’ll be! You lost a component and I see some trace damage!

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Not sure if this is repairable or not. It will likely need someone with deeper skills to fix.

Update (02/01/2022)

Here is the SATA port layout

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As you can see each port has its own power connection. So no need for a power spitter. The HDD port is a bit different as it has the added lines for the the drivers thermal sensor SMC requires access to.

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@danj - I just ordered a new logic board over eBay, price is not that bad, so, hopefully I can use this iMac again. By the way, per my another question asked earlier, the jumper placed by Apple on HDD power connector (next to SATA 0 data port), do you know if there is any particular reason why placing the jumper there?

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@lovecd - that was put on as you had an Apple SSD model as I explained in my answer.

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@danj - I'm curious to know if this is necessary, i.e, is there any impact if removing that jumper even though there is just one SSD (without installing the 3.5" SATA hard drive) was installed?

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@lovecd - SMC won't like it! You need it unless you put in a drive in the 3.5" bay at which point you'll need the thermal sensor.

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@danj - Thanks Dan!

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