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Model A1418 / Late 2013 / 2.7 & 2.9 GHz Core i5 or 3.1 GHz Core i7 Processor

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iMac chimes but no apple, black screen for 4 minutes, then login scree

I replaced an old HDD with a 1TB WD Blue SSD and after restarting I first thought I had not connected the display properly as it chimed, but was black screen. I disconnected and reconnected, still the same.

I reset the SMC and PRAM and after leaving the machine for about 5 minutes it suddenly produced a login screen. It then seemed to work normally.

Restarting after updating everything possible to update produced the same 5 minute wait to login. Trying to boot from a USB installer produces the same 5 minute wait before showing the choice of boot device

Connecting another monitor gives the same black screen on the second monitor. No output until after the login screen appears.

Putting the old hard drive back in produces the same symptoms.

Holding D and doing a hardware test gives a clean bill of health (LOL)

I’ve done dozens of these before with no problems and I’ve triple checked all the cable connections I can see to check.

How can I diagnose this fault?

Ответ на этот вопрос У меня та же проблема

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Did you try replacing the NVRAM (PRAM) battery?

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I hadn't thought of that. Big job to get to it.

Is there no way of telling the battery is needing replaced through any testing procedure? It would save a huge amount of work.

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Replaced battery, no change

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Did you find solution to this? I also replaced old hdd with sata ssd and have same symptoms on my imac 2015 21.5.

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Can you hold Command + V keys on power-up and see if it boots under verbose and if not where does it get stuck?

Also, you can try to boot to safe mode:

  1. Prompt your Mac to restart. If your Mac is currently on, you'll need to begin restarting it before you can access Safe Mode
  2. Press and hold the ⇧ Shift key. As soon as your Mac begins restarting, hold down the ⇧ Shift key and don't let go
  3. Wait for the login screen to appear
  4. Release the ⇧ Shift key
  5. Log into your Mac

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Verbose mode does nothing. The main screen stays black, the second screen shows a background wallpaper image after about 30 seconds. The main screen stays black for 5 minutes then the login screen appears

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The strange thing is, once started it behaves normally. But if you let it sleep, once woken, the second screen comes on and the main display stays black for another 5 minutes.

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It's a bit odd you cannot get a verbose screen to show. I am a little confused by this my first guess would be a bad Drive but as you say normal performance after it finally boots.

Maybe @danj might have some ideas? He helped me with a MacBook that kept going to sleep...

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Don't know if this helps, but with the display panel removed, the fourth diagnostic led did not come on. I probably didn't leave it for 5 minutes like that but should it be off with the screen removed?

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@gusgus67 - The 4th LED won't lite without the display plugged in.

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I would check the battery to make sure its good and with the battery connected check the voltage at the carrier.

Your system is loosing its NVRAM (PRAM) settings. Which is why it takes a bit of time to run through the config POST which only happens when you alter the RAM setup (or when the battery is bad)

Clearly this is a logic board issue with the power logic. You'll need to get the schematics to trace out the power rails.

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Yes, I think you're right. I'm handing this on to someone who can investigate this. Thanks

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Go to System Preferences > Startup disk > Select your boot disk and then press the restart button. your iMac doesn’t currently have a default hard drive selected that’s why it’s taking ages to detect it. if it’s currently taking a while to start up hold down the option key and select your drive.

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No, sorry, not that

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Handed over to someone to investigate the power supply and logic board. Thanks for all the comments

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Angus Stewart будет вечно благодарен.
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