Help my Imac 2009 blank screen

My late 2009 iMac works fine, even plays music, but screen is blank. When it starts up, it chimes, then the screen flashes white once then blank, no matter what I do. I did replace the graphics card a few years ago with same product when screen was getting black bits. The important thing is the whole screen flashes white then blank or black. I have backed up to external hd. I don't know how to connect to an external tv screen. Help would be amazing.

denyason said:

I don't know how to connect to an external tv screen. Help would be amazing.

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This is what I was going to suggest. Connnect the iMac to an external computer monitor or TV. To do this you need the proper video cable & adapter.

- Nick

Thanks I've just ordered one so I'll let all know when I've tested it. Question is once I set up an eternal monitor how do I ascertain what is wrong with my Imac screen. Sorry I'm pretty clueless.

Have you tried booting up using Safe Boot Mode to see if the problem persists???

Press and hold down the shift key immediately you hear the boot sound from a cold boot.





- Patrick
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Yes I have tried it but with a wireless keyboard and no luck.

denyason said:

Thanks I've just ordered one so I'll let all know when I've tested it. Question is once I set up an eternal monitor how do I ascertain what is wrong with my Imac screen. Sorry I'm pretty clueless.

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- If you get NO VIDEO on an external display (external TV or external computer display)...then the graphics hardware on the iMac is most likely faulty or failed.
- If you DO GET video on an external display...then the iMac's issue may be a failed display panel, bad video cable, or maybe if you're lucky...just something loose.

One other thing to try (to eliminate any software or OS related issues)...is boot the computer from an external storage device with a bootable OS on it.

Good luck,

- Nick

Hi all just got my cable yesterday and there is video on my tv, so my Imac is working fine underneath, seems the issue is the display panel. How much would you say it would cost to repair?

First, make sure it is the display. In a darkened room with your iMac on, hold a flashlight close to the screen. Can you see any video at all on the screen? If you can, it means the backlight in the display is defective. If the screen remains black with no detectable video, the display or internal display cables could be defective. In any event, you're very likely going to wind up spending more money to repair the iMac than it's worth. It's a decision you need to make. A 2009 iMac is going on 7 plus years old and is considered vintage by Apple which means they won't work on it.

As for cost, check eBay for parts. (display, cables, and anything else you may need)

Hi chscag. I only surf the web or watch videos on my Imac, I think it's still got life in it yet and looks very good and still stylish and relevant for my purposes. Plus I save near 2 grand to buying a like replacement. I tried it in dark, it's totally black, but when I pressed the button on back to switch off, the desktop came up for less than 1 second then black again? This I assume would indicate cabling rather than the display being damaged, maybe I'm wrong.

This I assume would indicate cabling rather than the display being damaged, maybe I'm wrong.

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Yeah, looks like you may have lucked out. My guess is that it might be a bad LVDS cable or another to the display internally. With a machine that's been around 6 or 7 years, the cables get brittle from the heat and have a way of failing internally. Be careful when you remove any of them - careful not to damage the connectors. I have inadvertantly broken several molex and otherwise connectors on electronic equipment by applying to much upward force. Buy a set of those plastic removal tools from ifixit or OWC before you dig into any repairs.

Thanks will do

This is weird so I hook up my tv to my Imac all great and I read something online. It tells to put Imac to sleep, I go safari: sleep via tv, sleeps then I press keyboard, Imac screen shows for 1 second then blank, on tv back on. So I play with the screen brightness, set it to lowest, sleep via tv, click keyboard and my Imac is working??? It seems to work for now on the lowest setting, tried brighter, it either goes off, then I need to make brightness lowest and sleep, wake up to fix, on brighter settings it will flicker. The probably is a temporary so hopefully there's enough info for you guys to ascertain what wrong with it.
Btw my Imac doesn't go to sleep if I press the button via the back.

Just to add. If I turn my Imac on, it stays blank, I have to connect to tv, put to sleep then it works again as my Imac on button doesn't put to sleep.