iMac doesn't turn on, please help!

[882476]

Hello,

I have a 2007 INTEL iMac 24" WHITE body not aluminum.

Serial #: W87030FPVGN.

My boss gave me this computer in hopes of being able to fix it. So hopefully with help from this forum I can do that! This is my first ever post on this forum.

PROBLEM: It wont turn on. I hear the fans and hard drive & everything else turn on but the screen remains pitch black. There is also no chime when the fans turns on. The power light is illuminated steady white.

If I try to turn the iMac on and off multiple times back to back over 10-20 times it will chime and the loading screen will pop up for 2-5 seconds then the screen goes black and nothing else happens no other noises. But the fans and everything but the screen turns on.

3 out of 4 DIAGNOSTIC LED'S are on. The 4th one is off all the time until the computer magically turns on after I try 10-20 times but as soon as it goes pitch black it turns off again.

PLEASE HELP!

 

[Cristian .b]

have you looked inside it? something is definitely busted inside there.

 

[jaxhunter]

Those had a tendency towards failed video cards. Should be on a replaceable daughtercard. As to where to get one, I don't have any idea. That unit is unfortunately considered Vintage by Apple and the stores won't be able to get ahold of the parts for them.

 

[macthefork]

It sounds like it IS turning on, if you can hear the fans and HDD. As mentioned previously, that model had problems with it's GPU (video card). The fourth LED indicates the GPU is not communicating with the LCD Panel. Since the third LED is lit, the Logic Board is communicating with the Video card. But, the videocard is not communicating with the LCD Panel. This could indicate lose or disconnected cabling to the LCD Panel, or more likely in this case, a failed video card.

If you have a second monitor you could try and connect that. But, if it's the video card, that won't work, either.

 

[882476]

Update: I removed the entire video card with the heat sink as well as the lcd and tried starting the computer up to see what diagnostic LEDs I get.

Before with the lcd and the video card connected LEDs 1,2, & 3 were green with LED 4 off.

NOW with the lcd & video card removed I started the computer heard no chime and LEDs 1,2 AND 3 were on.

LED 3 ( indicates that the computer and the video card are communicating. This LED will be ON when the computer is communicating properly with the video card.)

HOW ON EARTH can LED 3 still be on even though the graphics card is removed.

If I keep turning the machine on and off multiple times. I will finally hear a chime and only LED 1 & 2 light up with 3 and 4 off. Which is what I expected to see when I first turned it on after removing the LCD PANEL and GRAPHICS CARD.

PLEASE ALL THIS INPUT AND COMMENTS IS VERY HELPFUL. I WOULD LOVE TO HEAR WHAT YOU GUYS THINK.

From my opinion I think my mother board is shot. Since it's telling me that the graphics card is communicating with the motherboard even though there is no graphics card installed.

 

[jaxhunter]

Its possible that with the video card removed the system is defaulting to the integrated graphics card in the chipset or at least trying to. It can't use it but there is no way for it to be disabled except by the installation of the add-in video card.

All things being equal I would still look at the video card as the suspect component. The difference in price between a logic board and a video card is substantial enough that it may be worth the risk to try the video card first.

Replacing the logic board may simply not be worth the money or the time given the age of that machine. That being said, I probably would still try to repair it because I hate to see any possibly decebt Mac go to the graveyard before its time.

 

[882476]

I wish I had a spare graphics card laying around. Unfortunately I do not.

Is there anyways to test whether it's the logic board or the graphics card 100% before actually spending any money and guessing on a fix. I'm with you I would really love to fix this machine.

 

[jaxhunter]

Not really. You really do just have to swap the video card with a known good one.

 

[macthefork]

Well, I wouldn't usually post this. But, since you likely have nothing to lose I'll ask you: Have you thought about baking the graphics card at about 400ºF for about 10 minutes? No? I didn't think so.

In some cases where a graphics card failed due to the solder failing, this trick as apparently worked for some. It re-flows the solder if that's what caused the failure.

This you would certainly do at your own risk. Also, if you consider this, purchase some heatsink compound to use after the GPU has cooled, then clean and recoat the chip to heatsink area.

Here's one link where an iMac's video card was brought back into working order. You can also simply Google "bake graphics card" to see many success (and failure) stories.

 

[jaxhunter]

Unfortuantely in this case it is not a solder issue with the cards but rather something with either the video RAM or the GPU silicon. It is just something that needs to be replaced. The baking trick did work for the Mac Pro ATI Cards (I forget which one) but it won't work for this.