HELP: Dead Display but can Mirror

[Methanoid]

I picked up a cheap iMac 2.66 Core i5 (11,1 A1312 late 2009) but the display is dead. The machine lives and can use the miniDP to display on a PC monitor. But some clever soul decided it would be clever to wipe the HDD and clone the Mavericks installer to the HDD so I cannot actually load an OS and just boot to the installer and cannot wipe the HDD from that. I cannot boot a USB as I cannot seem to display the early boot screen to select a USB stick (or CD?)

Any ideas how I can get an OS onto this?

Also I need to diagnose the display issue. Obvious candidates are

Inverter Board - can I confirm easily with a multimeter (only shows voltage/current)?
The backlight circuit - somewhere?!
The LCD itself
The GPU (but that does drive an external display so presumably is alive??)

Any pointers gratefully receive. I hae the idea of just junking a good machine, which can also serve as an external monitor in Target mode (when display works)

 

[Nguyen Duc Hieu]

I picked up a cheap iMac 2.66 Core i5 (11,1 A1312 late 2009) but the display is dead. The machine lives and can use the miniDP to display on a PC monitor. But some clever soul decided it would be clever to wipe the HDD and clone the Mavericks installer to the HDD so I cannot actually load an OS and just boot to the installer and cannot wipe the HDD from that. I cannot boot a USB as I cannot seem to display the early boot screen to select a USB stick (or CD?)

Any ideas how I can get an OS onto this?

Also I need to diagnose the display issue. Obvious candidates are

Inverter Board - can I confirm easily with a multimeter (only shows voltage/current)?
The backlight circuit - somewhere?!
The LCD itself
The GPU (but that does drive an external display so presumably is alive??)

Any pointers gratefully receive. I hae the idea of just junking a good machine, which can also serve as an external monitor in Target mode (when display works)

1.
To install OS, you can remove the HDD, replace it with 1 SSD, then do a PRAM reset.
After PRAM reset, the machine will boot from the only bootable device, which is the USB installer (of High Sierra, I guess).
Or you can just plug in the SATA port one SSD with High Sierra pre-installed.
All can be viewed from the external display.

2. The LCD
To check the LCD, you can open the case and exam for physical damage: loose cable, burnt mark on the backlight powerboard, etc.
If you have another working 2009 or 2010 iMac, you can swap the LCD panel, the backlight board to verify each part.
Cheap things you can buy to check
1. Backlight board (about 12~15$)
2. LCD driverboard kit (25$)
3. Replacement LVDS cable: 8$.

 

[Methanoid]

Thanks, or I guess, just remove HDD, wipe in a PC and reinsert. But yeah SSD would be nicer.

No 2009-2010 iMac.

Are there no checks I can do with a MM on the Inverter board? And for Backlight board do you mean Inverter like this? https://www.ebay.co.uk/itm/281279547839

 

[Nguyen Duc Hieu]

Thanks, or I guess, just remove HDD, wipe in a PC and reinsert. But yeah SSD would be nicer.

No 2009-2010 iMac.

Are there no checks I can do with a MM on the Inverter board? And for Backlight board do you mean Inverter like this? https://www.ebay.co.uk/itm/281279547839

You need to check the actual inverter board inside your iMac, although they are compatible, the v-sync cable maybe different.

 

[Methanoid]

Ah, thanks... I opened it up and found the previous owner had been inside and had mucked some bits up. I straightened the pins on the main (largest connector) which was hanging loose not connected. Also a secondary small connector (that is in the top RHS as viewed from above) has metal connecting strips separated from the backing. I've just superglued them down. When dry I will reconnect it and with luck the screen will work!!

 

[Nguyen Duc Hieu]

Ah, thanks... I opened it up and found the previous owner had been inside and had mucked some bits up. I straightened the pins on the main (largest connector) which was hanging loose not connected. Also a secondary small connector (that is in the top RHS as viewed from above) has metal connecting strips separated from the backing. I've just superglued them down. When dry I will reconnect it and with luck the screen will work!!

That one is the v-sync cable.
I read somewhere that it won't affect the operation of the LCD much.
Anyway, it's quite cheap so I bought a pair for reserve.

 

[appltech]

FYI: when wiping Mac's HDD on PC make sure to select GPT (GUID) partition table.
Directly from Windows, or from existing macOS VM (VMWare Player. Oracle Virtualbox, etc)

 

[Methanoid]

All fixed. Previous idiot owner had torn the MAIN connector clean off. I straightened the bent pins and re-attached the connector, superglue holding the plastics onto main board. The small (V-sync) cable pins had also separated from plastic cable. Glued them flat and when dry, reconnected all up and machine is ALIVE! Now I can see EFI screen I can wipe HDD and install El Cap to make sure all is OK and then OpenCoreLegacy to Monterey.

Good to get it alive again. Thanks for the pointers anyway, good for my Mac education.

 

[Nguyen Duc Hieu]

All fixed. Previous idiot owner had torn the MAIN connector clean off. I straightened the bent pins and re-attached the connector, superglue holding the plastics onto main board. The small (V-sync) cable pins had also separated from plastic cable. Glued them flat and when dry, reconnected all up and machine is ALIVE! Now I can see EFI screen I can wipe HDD and install El Cap to make sure all is OK and then OpenCoreLegacy to Monterey.

Good to get it alive again. Thanks for the pointers anyway, good for my Mac education.

Great news to hear!
I would suggest you install High Sierra and all of its updates before installing Monterey.
SSD is a must for Monterey.
Stock graphic card won't perform very well on Monterey.
Try getting an M6100 MXM card if you can find one at reasonable price (<40$)
Otherwise, just keep the iMac as a monitor to save cost, if you already have another Mac to use.

 

[wolf1734]

hello I have a screen problem on my 27" iMac from 2009. the screen lights up a bit but I can't see anything on it? does it work on an external screen? I changed the invent card but the problem is still there I tested the screen on another iMac and it works, do you have an idea thank you

 

[Nguyen Duc Hieu]

hello I have a screen problem on my 27" iMac from 2009. the screen lights up a bit but I can't see anything on it? does it work on an external screen? I changed the invent card but the problem is still there I tested the screen on another iMac and it works, do you have an idea thank you

On the external screen, check if your iMac recognizes both screens.
If it does, then the issue might be a knocked-off transistor on the logicboard. (If your iMac was opened before to replace the GPU).

https://forums.macrumors.com/attachments/mosfet-jpg.1784207/

 

[Nguyen Duc Hieu]

Another case

https://forums.macrumors.com/threads/solved-two-imacs-2009-black-screen-backlight-ok-gpu-ok-four-leds-on-any-ideas.2351165/

 

[wolf1734]

Hello, on a 27" iMac the screen stays on a bit but nothing is visible, however it works on an external screen. Could it be from the video card or something else? Thank you for your answer.