# Imac 20 inch Mid 2007 black screen HELP!



## MacGuiver (Sep 6, 2002)

My sisters imac suddenly will not boot.

Its a mid 2007 model 20inch

Symptoms: When you go to start it up the fan runs but no startup chimes are heard and the screen remains black.
I opened it up to check the status of the 4 diagnostic LEDs. LED 1,2 and 3 light up but LED #4 does not.

This is a troubleshooting guide I found online in the event that LED 4 is not lighting up:



> LED #1 + LED #2 + LED #3 + LED #4 = Power available, system is powered on, video card found, and internal LCD found.
> 
> If fourth LED is not visible after power on:
> 
> ...


I don't have the proper cable to hook this up to an external monitor but if it was simply a failed display, wouldn't the mac still chime at startup or will it not chime at all if there is no working display? This one isn't chiming at startup and the screen is black.

Anyone with experience with this your input would be greatly appreciated. If I could isolate the problem and the part is not too expensive I'd attempt the repair myself.

Thanks
MacGuiver


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## eMacMan (Nov 27, 2006)

My first guess would be the nvram battery. By now it should be completely dead. Not sure how accessible it is. If you are lucky it will be located near the RAM modules and easily reached. Otherwise you may need outside help.

For all of the advances in Mac computers over the past 20 years, this little battery can still entirely disable your Mac.

EDIT: Sorry but it would seem you are not so lucky. 
Installing iMac Intel 20" EMC 2133 and 2210 PRAM Battery - iFixit

Still in terms of iMac repairs this one looks possible, but not nearly as easy as it should be.


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## MacGuiver (Sep 6, 2002)

eMacMan said:


> My first guess would be the nvram battery. By now it should be completely dead. Not sure how accessible it is. If you are lucky it will be located near the RAM modules and easily reached. Otherwise you may need outside help.
> 
> For all of the advances in Mac computers over the past 20 years, this little battery can still entirely disable your Mac.
> 
> ...


Thanks so much EMacMan!

This is something I could easily swap out and it won't cost me a bundle to try. I'll give it a go. It makes perfect sense this could be possibly be the culprit. This computer has only seen light sporadic usage in its 5 years and I find it hard to fathom its burned out. 

Cheers


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## MacGuiver (Sep 6, 2002)

Tried the battery swap. No luck.
Thanks just the same eMacMan. It was worth a try. I think a trip to the apple store is coming.


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## pm-r (May 17, 2009)

FWIW, my mid-2007 24" iMac suddenly died in the afternoon while I was using it about a year ago with a black screen, just like someone had pulled the power cable.

I don't recall all the symptoms and things I tried, but I finally concluded that that the hard drive had completely died, which it had. Replaced the HD and all is still working well.

I never bothered looking at any LEDs. But will it boot from the install disk or from a bootable hard drive?


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## eMacMan (Nov 27, 2006)

MacGuiver said:


> Tried the battery swap. No luck.
> Thanks just the same eMacMan. It was worth a try. I think a trip to the apple store is coming.


Sorry that was not it, as it certainly could have created the problem and as you said an inexpensive fix. In any case after checking the power cord it is the second thing to check.

Was the screen flickering or intermittently blacking out and coming back on before the failure?

It does not sound like your sister would have a lot of USB or FW peripherals attached, but disconnecting all of those except KB and Mouse might be worth trying. Much less optimistic about that idea. 

If the battery is OK I am sadly leaning towards video card or logic board issues, keeping in mind what pmr said about bad HDs being known to cause a similar effect. 

Unless you have a spare HD floating in your spare parts drawer, probably time to talk to the experts.


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## eMacMan (Nov 27, 2006)

Note; depending on OS and computer model. If the admin account had volume set to mute at last shutdown, then you may or may not hear a start-up chime even if the computer is functioning normally.

Perhaps one of your Windows friends has a small monitor you can borrow. Cable adapters are not horribly expensive. Might also be able to borrow one from the nearest Apple dealer if you have a good relationship with them. Would at least allow you to further isolate the problem before making a decision as to deep six or repair.


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## dona83 (Jun 26, 2005)

If you have a backup drive, hopefully you do, you could try to boot off that.


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## pm-r (May 17, 2009)

Also try an SMC reset and a "PRAM" (NVRAM )reset I forgot to add as a suggestion.

Intel-based Macs: Resetting the System Management Controller (SMC)


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## eMacMan (Nov 27, 2006)

pm-r said:


> Also try an SMC reset and a "PRAM" (NVRAM )reset I forgot to add as a suggestion.
> 
> Intel-based Macs: Resetting the System Management Controller (SMC)



Changing the battery should have forced the nvram reset.

Looks like the SMC reset would also have been accomplished when he unplugged the computer to change the battery.


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## pm-r (May 17, 2009)

Yup, you're correct - it _*should*_ have.


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## MacGuiver (Sep 6, 2002)

Thanks for all the help guys! Much appreciated. 
My gut says logic board but hopefully I'm wrong. I didn't try booting for a DVD since I don't suspect the computer is getting far enough along to get to that point where I could select it as an option. NO chimes and I think the only thing operating is the fan. I have an identical imac to hers and its not making the same sounds at startup as mine. I think the fan is the only thing coming on. At this point I'll leave it to the pros.


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## broad (Jun 2, 2009)

video card, logic board


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