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Model A1225 / Mid 2007 and Early 2008 / 2.4, 2.8, or 3.06 GHz Core 2 Duo processor

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Why will my machine not re-start?

I have a similar issue to Powers up, no chime, three LEDs, then shuts off..  but with a very slightly different LED sequence.

Early 2008 24” 2.8 GHz Intel iMac; 4GB RAM; EMC No. 2211; Model No. A1225; OS X El Capitan with latest (last) security update (15G22010).

The machine was shut down during a recent vacation and on return it would not start normally. After re-setting SMC or PRAM it would run without a problem. But it required such re-setting after every shutdown.

Yesterday the machine worked fine – it had been on continuously for several days after starting with a PRAM re-set. I reinstalled OS X El Capitan, keeping the user data. Everything looked good and I  subsequently closed down and restarted the machine normally 4 – 5 times (no re-sets).

Today the machine would not start. Resetting the SMC and PRAM does nothing. I replaced the PRAM battery. No change.

Symptoms: After pressing the power button I hear a fan operating and the chime starts; however the chime is cut short and the fan noise stops. The machine cannot be re-started until the mains plug is removed and replaced.

LED 1 lights up when it's plugged in. When I push the power button LEDs 2 and 3 and 4 light up sequentially. But as soon as LED #4 lights up it turns off, followed very rapidly by LEDs 3, 2 and 1.

Long story but a short question: Is the power supply the culprit, as in Steve Godun’s case, or, because LED #4 is coming on for a split second before all LEDs shut down, is something else in play?

Update (06/04/2019)

Bulge at end of capacitor C209 second from right:

Block Image

Maybe slight bulges at end of two black capacitors C214 & C215:

Block Image

Discoloured coil:

Block Image

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The two caps are indeed need to be replaced! Or, just replace the full PS unit.

The coils look OK, the coloring of the wire has to do with the gage of the wire and the supplier.

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Yes, you’ll need to start with replacing the power supply. Sadly, sometimes surges or lighting strikes damage more than just the power supply. Your system is old enough to have been effected by Capacitor Plague. Let’s hope its only the PS!

  • Power Supply 240 Watt - Apple P/N 661-4422
  • Power Supply 250 Watt - Apple P/N 661-4478

Here’s the iFixit guide to get into the system iMac Intel 24" EMC 2134 and 2211 Hard Drive Replacement Once the display is pulled off you can access the power supply. Inspect the caps to see if the issue is leaking if it is that’s a clear sign power supply might be fixable replacing the caps.

I would also make the effort to get a good surge suppressor or better yet a good UPS so the system as well as all of its peripherals are all serviced by it. I would also check the wall power outlet making sure its properly wired and the ground leg is present and working. You should also check your breaker panels wiring to ground making sure the connection is solid and not corroded. Make sure the connection is to a metal pipe leaving your home or goes to a one or more grounding rods.

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Many thanks, Dan, for your prompt and comprehensive reply.

It occurs to me that although the text was ok my question is not accurately phrased: when it was operating the machine restarted correctly every time via the 'Re-start' procedure. The problem was limited to re-starting when the machine was switched off entirely.

Does that change your advice in any way?

I think the mains power supply integrity is ok, I have a UPS in place and run my other machine from the same power source. I'm tending towards the capacitors, thanks for the Wikipedia link. I'll let you know what I find when the additional tools arrive to access the power supply.

By the way, as best I can see the Apple Part Number for the 250 Watt power supply for this machine (EMC 2211) is 661-4665 (661-4478 seems to be for the EMC 2134 variant). Probably hard to source these days.

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If you are un-plugging the power cord or have a Surge suppressor which cuts the power fully or kills vampire power then you could have a bad PRAM battery. iMac's use a vampire load on the power line to supply the clock & PRAM battery. To test go into the Preferences Date and Time and uncheck 'Set date & time automatically' make sure the date & time are correct and then shutdown your Mac and pull the power cord for the night. Then in the morning plug it back in and check the date & time is it correct? If not change the battery. Its located on the main logic board CR button battery.

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Thanks Dan. It was precisely this test that I wanted to run but I could not start the machine from cold to complete the test. I replaced the PRAM battery but the machine still would not start.

I have now removed the power supply and found that, although not leaking, one of the five larger capacitors (C209), second from right) has a slight bulge in each of the three segments at the bottom.

I also noticed that two black capacitors (C214 & C215) near the 12-pin screen plug might have slight bulges at their ends.

Finally, I also noticed that the largest coil at the other end of the board is discoloured.

I'll try and upload three photos, at the moment I don't see how to do that .......

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Time for a new PS or if you can replace the bad caps!

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Thanks again, Dan. I'm having difficulty sourcing reliably Apple P/N 661-4665 (EMC 2211 machine). In your original reply you recommended Apple P/N 661-4478, which is easier to source. Is that part interchangeable with P/N 661-4665?

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