iMac 2009 black screen

[halo80]

I need help with my Fall 2009 iMac which sounds like it’s turning on and running but the screen remains black. I can’t remember the last update that I applied but it was probably El Capitan.

Both my wireless keyboard and mouse are blinking at me so they’re probably not synced anymore to it. I have it connected to an external monitor via a mini-Display port cable. Any ideas/recommendations? I’m not opposed to buying a kit to crack it open.

 

[Bigwaff]

I have it connected to an external monitor via a mini-Display port cable

It’s not clear from your post whether the external display is also black like the built-in display.

 

[halo80]

It’s not clear from your post whether the external display is also black like the built-in display.

Oh right - The external monitor is also black.

 

[Nguyen Duc Hieu]

There are two models iMac 2009:
iMac early 2009 (black back)
iMac late 2009 (aluminum back)
Which one is yours?

My hope is iMac late 2009 with a dead GPU.
Because if it's the early 2009, the fix will cost more due to rareness of parts.

 

[JinxVi]

I need help with my Fall 2009 iMac which sounds like it’s turning on and running but the screen remains black.

If you hear the startup chime it indicates that at least a part of the hardware is okay.

Your PRAM battery might be dead.

Running an Apple Hardware Test might help to identify the problem.

And you should switch to a wired USB mouse and keyboard while troubleshooting.

 

[Nguyen Duc Hieu]

If you hear the startup chime it indicates that at least a part of the hardware is okay.

Your PRAM battery might be dead.

Running an Apple Hardware Test might help to identify the problem.

And you should switch to a wired USB mouse and keyboard while troubleshooting.

How can he run the Apple Hardware Test with a black display?

 

[JinxVi]

How can he run the Apple Hardware Test with a black display?

Maybe connect it to an external display via Mini DisplayPort.

 

[Nguyen Duc Hieu]

Maybe connect it to an external display via Mini DisplayPort.

In post #3 he said the external display was also black....

 

[JinxVi]

In post #3 he said the external display was also black....

This would suggest that it's not a problem of the display panel itself. All you can do is disassemble the iMac and swap parts with another old iMac, until you have a better idea of which part causes the problem.

 

[Nguyen Duc Hieu]

This would suggest that it's not a problem of the display panel itself. All you can do is disassemble the iMac and swap parts with another old iMac, until you have a better idea of which part causes the problem.

Then why did you suggest him to run Apple Hardware Diagnosis on both pit black displays in the first place?

 

[JinxVi]

Then why did you suggest him to run Apple Hardware Diagnosis on both pit black displays in the first place?

Didn’t think that through. 😅

Can you run the Hardware Test remotely? 🤔

 

[Nguyen Duc Hieu]

Didn’t think that through. 😅

Can you run the Hardware Test remotely? 🤔

Not possible when the displays don't show anything. To remote control the iMac, it must be set in advance.

 

[halo80]

This would suggest that it's not a problem of the display panel itself. All you can do is disassemble the iMac and swap parts with another old iMac, until you have a better idea of which part causes the problem.

This is what I was fearing but expecting. Thanks!! Much appreciated!