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BlueMacawBird

macrumors regular
Original poster
Jun 28, 2019
105
23
Washington, D.C. USA
I recently added an iMac 11,2 to my pile. The machine ran fine for several days, using SL and HS volumes on the internal HD. It ran really well, but I noted that it also seemed to run hotter than I would have expected of an i3. In any event I wanted to migrate data from another machine to the HS volume and ran Migration Assistant last night. MA started and ran normally. But this morning I found that MA was hung, and it had failed to complete the migration. I gave it a bit more time and finally restarted the machine. When the machine came back on it beach balled, and then nothing else happened. So now all I get is a blank white screen. The machine bongs at startup. The only startup key combinations that it responds to is an NVRAM reset, so I can get it to bong as many times as I want. But still all I get is a gray screen and it never continues to an Apple logo. No other startup key combination works. I also tried connecting it to another machine, and starting it up in target disk mode. That also did not work. I've tried all the startup key combinations on my list and none of them work except the NVRAM reset. I also of course unplugged it and let it sit for a half-hour.

So, how do I get this machine to complete it's boot process and come back to life?

Thanks,

John
 

mdgm

macrumors 68000
Nov 2, 2010
1,665
406
So this is the 21.5" mid-2010 iMac?

Are you able to boot it off the install DVD into Apple Hardware Diagnostics?

Or off a USB key using Apple Service Diagnostics for your machine or a bootable USB key installer?

It could be a failed graphics card I guess. Though if that's the problem it is a complicated repair.

You could also check to see if the memory (RAM) has come loose (an easy thing to check on this model as it has a memory access panel unlike the 2012 and newer 21.5" iMacs which require the whole machine pretty much to be dismantled to replace the memory).
 

BlueMacawBird

macrumors regular
Original poster
Jun 28, 2019
105
23
Washington, D.C. USA
It is indeed the mid 2010 21.5" iMac.

I did not receive any of the install DVDs with it. I wish I had the Apple service diagnostics but of course I don't.

I thought about the failed graphics card; I had a 27" 2011 iMac and this whole family of iMacs suffers from graphic card problems. That'll total the machine and I wrote off my 27" machine after two graphic card failures.

But there is progress. It is now running Internet Recovery. Which suggests that the disk did die. I would have expected to see a folder with a question mark indicating that no bootable volume had been found, but all I got was a blank white screen. Internet Recovery is of course very slow and I'll get back with an update tomorrow after it finally loads. In the meantime I'll prepare a new HD since it is pretty clear that one is going to be needed.

Thanks,

John
 
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mdgm

macrumors 68000
Nov 2, 2010
1,665
406
Considering the age of the hard drive that's hardly surprising, I guess. I have four mid-2011 iMacs and none of the hard drives have failed yet, but it's only a matter of time before one of them goes (amazingly none of the GPUs have failed, but I'd probably put that down to pushing the machines to their limits very much).

I would put a SSD in if you're going to replace the HDD. An SSD will make the computer feel a lot quicker. If you don't get a thermal sensor cable you'll need to use Macs Fan Control to control the fan speeds.

A 2.5" SSD is also going to run cooler than a hard drive. If you intend to keep the machine a while I'd go for an SSD designed to sustain the performance over the whole drive with say a 5 year warranty. Some of the cheaper options can slow down a lot as the drive fills up or have more limited write cycles.

If you don't want to pay for a SSD big enough to store everything you can use an external drive to store data that won't fit on the SSD though you would be limited by the slow IO by modern standards of the external ports. FW800 would be the fastest of the external ports. I have an early 2009 Mini booting off a FW800 SSD and it feels a lot faster than booting off the old internal 5400 RPM HDD.
 
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BlueMacawBird

macrumors regular
Original poster
Jun 28, 2019
105
23
Washington, D.C. USA
Time for an update. The machine received a new 500GB SSD and is running fine on SL and HS. I found the machine to be particularly dirty when I opened it, with the fans heavily clogged with dirt. I chased out all the dust bunnies and did my best to blow out every place I could. It now runs much cooler.

As I mentioned in an earlier post, I had a 27" iMac of the same vintage, and when it died I salvaged what I could from it. That included an OWC thermal sensor dongle, and amazingly I remembered that I had it and found it in my stash. So I did use it, only to find that the machine did not care and wanted to run the HD fan faster than needed. So I did download the Mac Fan Control utility that was recommended and that solved the problem. I really like the utility and it is a good way to keep an eye on temperatures.

One of the system temperatures that Mac Fan Control reports is for the "Platform Controller Hub Die", and I don't know what that is. The reported temperature for it is always 138 degrees F which makes no sense. I suspect that this is some kind of bogus item and I'll ignore it, unless someone can explain it to me.

And, one last observation. When the HD in the machine died, I would have expected to see a screen at startup that showed a classic symbol like a blinking folder, or a question mark, indicating that no bootable media had been found. I only got a gray screen. Also, when it died there was a bootable HD attached via USB. The machine did not try to start from it, and it should have found that and started from it. All in all the way the machine failed made diagnosing its problem unnecessarily difficult.

Thanks for your help in getting this iMac back up and running; it is a fun and useful machine and I'm glad to add it to my accumulation of vintage Macs.

John
 

DeltaMac

macrumors G5
Jul 30, 2003
13,490
4,416
Delaware
That Platform Controller Hub Die is a sensor on the hard drive - which you replaced with the SSD. The drive controller sees that sensor as an open circuit, resulting in a default output. That's where the 138 degrees comes from, and it's an SSD now, not really bothered by that "incorrect" temp value.
There's a couple of different thermal sensor cables. I wonder if your 27-inch iMac was actually a 2011 (which uses a thermal sensor cable different from one that works with 2009/10 iMacs - and still leaves your hard drive fan on a 2010 iMac running too fast.
And, not a big deal if you are OK with using software to control your fans.
Some here are not big "fans" of that solution - but it's just that, a solution.
 

nambuccaheadsau

macrumors 68020
Oct 19, 2007
2,024
510
Blue Mountains NSW Australia
Go to this Github link and download the version of Apple Hardware Test you want, place it on the desktop, pop in a thumb drtive, format it and drag the icon to the drive and burn.

 
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BlueMacawBird

macrumors regular
Original poster
Jun 28, 2019
105
23
Washington, D.C. USA
Thanks, DeltaMac, for your info about what the "Platform Controller" is. So now I can disregard that line in Mac Fan Control.

And you're right, the thermal sensor cable came out of my dead iMac 12,2, Mid 2011 machine. I did not think there would be different versions of the cable. Considering the PITA it is to open the machine (old arthritic hands do not easily manipulate the screen connections necessary for removal) I'm going to leave it as it is. I would prefer not using the utility, but it does solve the HD fan problem.
 
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