Chosen Solution
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:
Maybe slight bulges at end of two black capacitors C214 & C215:
Discoloured coil:
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 661-4422Power 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.
