Mac Desktops forum


iMac No Display

by ac1818 / December 26, 2012 10:20 AM PST


I have an iMAC (20 inch I think early 2008 model) which turns on, but there is no display. I can hear the startup chime and the fans starting, but the display is continually blank. I have tried resetting PRAM & SMC and have replaced RAM.
Any suggestions?

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All Answers

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I had one like that,
by mrmacfixit Forum moderator / December 26, 2012 9:29 PM PST
In reply to: iMac No Display

turned out to be the graphics board!

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I see
by ac1818 / December 27, 2012 8:06 AM PST
In reply to: I had one like that,

Thanks for your response. How did you determine that it was the graphics board? Any suggestions to determine what may be the cause and anything I can try?

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Try connecting to that iMac with another Mac,
by mrmacfixit Forum moderator / December 27, 2012 9:10 AM PST
In reply to: I see

if there is one available.

My iMac was under warranty so I let the local Authorized Service Provider figure it out.

Plugging a second monitor in and getting no picture there kinda rules out the dead LCD idea and points at the graphics card.


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Yes I have another Mac and mine is not under warranty
by ac1818 / December 27, 2012 3:32 PM PST

By the way if i turn the iMac on, and press the volume up and down keys I can hear the standards sounds of the volume increasing and decreasing

I have another mac, But how would I attach another iMac to this iMac. What cable would I use?

I could try a secondary monitor, but I do not currently have a mini-dvi to vga adapter. I will see if I can find one

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A length of ethernet cable will do it, but
by mrmacfixit Forum moderator / December 27, 2012 8:41 PM PST

having the two Macs on the same network is the preferred method.

Can the second Mac access the internet at the same time as the other. (or the other used to when it was working correctly?)

Apple service guy said that $300 would be about the cost of replacement out of warranty.


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Sorry. Not sure what you mean by that question exactly
by ac1818 / December 28, 2012 5:54 AM PST

Thanks for your response. I have Ethernet cables
The second Mac is also a 2.4ghz Core 2 Duo iMac. Well it should connect to the internet as it was working fine before.

So I can connect both iMacs to the internet using and ethernet cable, but how would I then set it up. Please advise

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To connect both iMacs to the internet at the same time
by mrmacfixit Forum moderator / December 28, 2012 7:26 AM PST

you must be using a home network.
Modem > Router > and two Macs.

On the working iMac, turn on File Sharing.

Still on the working iMac, and with the defective one turned on, go to the GO menu (top of screen) and choose Network.
You should now see any computer that is connected to the same network as you are.
Hopefully you will see the defective machine there.
Double click it and choose Connect As. Put in the username and password of the usual Admin account on that machine. (This is not necessarily the same username and password as the one on the good machine)
Can you access the machine?

If so, go to System prefs and make sure that only a single monitor is selected and anything else you can find.

How did it go with the second monitor test?


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by ac1818 / December 28, 2012 8:48 AM PST

Trying that now
Still trying to find a mini dvi adaptor to go ahead with the second monitor test

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It worked
by ac1818 / December 28, 2012 9:33 AM PST
In reply to: Reply

I can access the machine through file sharing. Any suggestions?

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(NT) Still leaning to the graphics card
by mrmacfixit Forum moderator / December 28, 2012 10:49 PM PST
In reply to: It worked
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by ac1818 / December 29, 2012 7:15 AM PST

Thanks so much for your help so far
Atny way to diagnose the issue? I can take it a part and see the diagnostic lights on MLB if that will help. I was wondering if it could be the inverter board connection or the display itself?

I was reading a similar thread, however my issue is a bit different as I can access the broken iMac on the Network meanings it still turns on.

PS: How did you know Apple charges $300 if it is out of warranty?

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How much it cost,
by mrmacfixit Forum moderator / December 29, 2012 10:45 PM PST
In reply to: Okay

was determined by the AASP where I live. The price did not come from Apple, just from him.

The Graphics Board lives underneath the logic board and so the entire machine has to be taken apart to access it.
Whether it is actually replaceable is another question, as is the availability of a compatible card.

As we know, your machine is functioning perfectly. It just has video issues.

How are we coming along with the second monitor test, which would eliminate the LCD on the iMac.


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I think we can continue here
by ac1818 / December 30, 2012 6:17 AM PST
In reply to: I had one like that,

Yes. I agree with your statement. Thanks for your help so far. Will it help if I check the diagnostic lights to verify what the issue could be?

I still want to try the second monitor test, but as I understand I need a mini-DVI to vga or dvi adatper. Am I right? If so I am still looking for it.

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Regarding the adapter,
by mrmacfixit Forum moderator / December 30, 2012 7:49 AM PST

available at the Apple Store or Amazon

I do not know what the diagnostic lights display when the graphics card is defective, so pulling the machine apart to see that would not help.

There used to be another Apple Authorized Tech who frequented these forums, possibly he will comment on the diagnostic lights.

Don't hold your breath though


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Will get an adaptor
by ac1818 / December 30, 2012 8:19 AM PST
In reply to: Regarding the adapter,

Will try the second monitor test. I think Jimmy Greystone might be able to comment on this.

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(NT) that's the guy
by mrmacfixit Forum moderator / December 30, 2012 8:29 AM PST
In reply to: Will get an adaptor
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