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Model A1224 / Mid 2007 and Early 2008 / 2, 2.4, or 2.66 GHz Core 2 Duo processor

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iMac won't start after HDD replacement - no chime, black screen, DVD

(originally posted as a comment on this thread My MacBook won't boot, no start chime, just the DVD spinning sound. but my hardware and symptoms are different and caused by my own hdd replacement attempt hence a separate question)

On a 2007 20" iMac after attempting to replace the hard drive - I can't restart the Mac. The original problem was definitely a bad hard drive - I could start and boot from CD or an external drive). Immediately upon closing the case and turning it on I got a black screen, no chime, both fans start briefly, dvd ticks a couple of times, then it repeats itself indefinitely until I pull the plug.

Tried all the key combinations for clearing NVRAM and holding power button down, etc.

Gave up and put it away for 3 mths (have a new mb pro :))

This is clearly some mistake I made in taking it apart and putting it back together (following iFixit instructions here iMac Intel 20" EMC 2133 and 2210 Hard Drive Replacement, since it worked fine but for the hard drive before.

Trying to fix it again.

First I removed the new HDD to see if that was it.

I have a Time Machine backup attached by FW, and even with no HDD I should be able to boot past this point, right? I mean I should at least get past a black screen? So from here on, I'm working withOUT the internal HDD attached at all.

Anyway I removed the RAM on advice in the thread above above - and ...+something+ happened… With no RAM in I get the no-RAM single beep and it seems to go a lot further: fans stay on, lots more DVD noise seems to be trying harder almost like it's actually going to boot, but in the end it gets no further and the screen never changes from black.

Adding the RAM back one chip at a time puts me back to the original problem... Even with just one RAM module in one slot (either one, tried both).

Pulled out the RAM and put it back several times no luck. Also no luck with any of the keyboard options while the RAM is out (I tried holding down T or R or C or Eject with a regular apple USB keyboard while booting - no diff)

Any ideas?

Also, what does the fact that it seems to get further with no RAM mean? Does it just mean that the real problem occurs after the RAM check? Or is the problem related to the RAM?

Note that the RAM was fine before I replaced the HDD as was everything else.

I looked for loose connections - and cant find any. Perhaps I plugged the connections between the screen and the MOBO back wrong? What else?

[UPDATE after Answer below]

Thanks for the tip on the LEDS. I have the left three lit and steady, which apparently means all is well but for the communication with the LCD panel. Which kind of makes sense since it is dark.

I tried an external monitor: it also stays dark. Not sure however, if this is not simply because it can't boot to the point where it could drive an external monitor.

I tried plugging back the old - bad - hdd to see if it made a difference (that disk was faulty of course, but I got further than this _before_ I removed it, so I wanted to try to get back at least that state). Makes no difference - so it's clearly something I did wrong in dismantling/assembling.

Note that my "good" disk has never been formatted, so it would not be bootable. And I can't find my original CDROM (I suspect it's actually in the drive but I can't tell - and its been a few months since I gave up on it :))

So where am I now:

- No disk/bad-disk/good-disk-unformatted makes no difference

- removing RAM causes it to try harder (it seems) but fails with missing RAM (all combinations of RAM in/out tried)

- External monitor makes no diff - not sure if that's significant

- Looks like I broke the connection with the LCD during assembly

Any ideas what to look for here? One thing I'm not sure about is whether I have the Inverter Cables connected properly. Could it be that?

Could it be one of the heat-sensors: will it fail like this if they are not connected?

Any other ideas?

thanks again

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I don't know if you were able to fix the display issue or not but I ran into a similar problem as you with only 3 LEDs lighting up on boot, after I upgraded the processor, airport extreme card and swapped the HDD for an SSD.

I also thought that I might have broken the LCD connectors or might have done something to damage the logic board but that did not turn out to be the issue. It felt strange having a damaged logic board GPU or LCD just by taking it apart. Anyways, the fix that worked for me was reseating the GPU.

So I basically took the whole thing apart again and took off the GPU by removing its heatsink and then added fresh thermal paste. Although I hadn't touched the GPU earlier I had a feeling that this had to be the culprit (Maybe it had come loose or something). I then put everything back together making sure that the screws were properly tightened and It powered right back on with the 4th LED lighting up and Chime.

So basically I went from first 3 Solid LEDs, no Chime, spinning fans, black display to 4 Solid LEDs, Chime, fans spinning and display powering on. The machine is working fine now. My iMac model is mid-2007 20". I hope this helps!

Other fixes I tried that didn't work:

  • Resetting the SMB
  • Resetting the PRAM
  • Replacing the battery
  • Fidgeting with the display connector / Inverter cables on the LCD
  • Taking off the LCD ribbon cable and reattaching it
  • Reconnecting the original HDD and Wireless/BT cards

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Is this still working for you or have you had to replace the video card?


Yes, it is still working perfectly without any issues.


Update: Still going strong 2 years later


Got light 1-2-3 on and the last one is off ? Was your problem from the 4 th one too


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No - TimeMachine is restore-ware, not a boot able clone.

What do the LED diagnostics tell you?

Have you tried to boot the good HD using an external monitor?

If this answer is acceptable please remember to return and mark it.

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How do I read the LED diagnostics

Also -haven't tried an external monitor but the fact that the fan stops after about half a second of trying to spin up makes me think its never going to get to display anything on the screen - or is that normal?

Are you saying that without a boot drive it's normal that it will do this, or normal but should show something on the monitor meaning the screen is not connected properly?

As for a good HDD - I don't have one: the new one is blank the old one is busted - perhaps I should shove in the original boot disk?


In order for the machine to boot it must past POST (power on self-test). It MUST HAVE OK power, RAM, Boot volume and no critical damage to the Logic Board. You can use an external Video Display and Keyboard mouse or trackpad... to pass POST. IF you can boot to an install volume and format the new HD and install an OS you can restore from TimeMachine. See this for Diagnostic LED's


No dice - see my update above (sorry, bad form to answer up there but the answer was too long for a comment apparently). I checked the leds - it looks like there's a problem connecting to the LCD - what could I have done wrong? What can I check?


No video on external points to a blown VGU/VGC... not just the internal display chain. In fact if it is the VGU/VGC your display etc. may be OK. (this is where I'd start) if you think this box is still worth more time and $ (it's getting pretty long in the tooth as computers go) Only you know how much you want to sink into it as opposed to takining the repair funds, some more $ and getting a new box. (You may recoup some costs selling the old box as is on e-bay).


Thanks for bearing with me.

One thing I don't understand: you're suggesting it's the video card right, but the LEDs reference you gave me says that the 3rd LED indicates a problem with the video card, and the 3rd LED is just fine.

Of course the 4th LED (off) indicates failure to communicate between the video card and the LCD, so maybe it's _that part_ of the video card. But couldn't that be something else? A cable or something?

I do want to keep going with this - I don't need the machine but its a shame to toss it out. Most of all though, other than the HDD problem, it *worked fine before I opened it*!!

thanks again


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