Released June 2012 / Core i7 processor with Turbo Boost / Up to 1 GB DDR5 Video RAM

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How to detect and replace a failing logic board capacitor?

Hello !

I'm struggling with my sister's maccintosh, I'm an IT engineer with some small electrical knowledge...

Failure symptoms are :

  • (A) When turning on the computer, everything is normal for 0.5 seconds (all the peripherals are powered), then everything shut down -> The computer does not boot.
  • When battery charger is plugged, the computer try to turn on and loop each ~ 3 seconds on symptom (A)
  • Every ~ 40 hours, the computer does a successful boot.
  • During a successful boot, everything works well, RAM / Disks / etc are OK, Syslog is OK, software is OK
  • The logic board have same issue without peripherals plugged in (Disks, RAM, trackpad, keyboard, WiFi etc.)
  • Both RAM & optical drive have been replaced 1 month ago for 8 GB RAM & SSD (with compatible units)
  • Reset SMC works but does not resolve issue
  • The logic board have no sign of grilled components

If I send the computer to Apple (after cleaning my hardware changes), they will surely detect a logic board failure and charge me for ~400 USD to replace it.

I want to repair the logic board, not buy a new one. I think this mess is coming from a capacitor that have some issue to full charge. IMO, that would explain the ~40 hours to wait for a successful boot.

  • Could my conclusion be correct ? (Capacitor failure)
  • How can I check which capacitor is failing ?
  • Can I try to replace it ? (I love to repair 'hard stuff' like this)
  • Did you have some nice gifts for Christmas ?

Thanks for reading, sorry for bad english (not my primary language) and happy holidays (if you have some)

Matthieu

Answered! View the answer I have this problem too

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@hmatthieu what is the exact model of your computer? If you can let us know what the 820-XXXX (820-2915?) number on your logic board is. There might be a possibility we can help you out a bit further.

You might also consider posting some good images of your logic board with your question so we can see what you see. Use this guide Adding images to an existing question for that.

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All right, I'll add all those information this weekend. Thanks for your help !

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2 Answers

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Capacitors are typically the most prevalent component on a logic board. However, an Apple logic board typically does not have electrolytic capacitors, which are the kind that can dry up and be problematic (capacitor plague). Apple only uses high quality components so the chances that your problem is caused by a "bad" capacitor are pretty low.

Ideally, you need to have this logic board looked at by a reputable repair shop that can do board-level troubleshooting.

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My experience with Apple geeks is they dont do board level troubleshooting, they usually just recommend replacement.

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Thank you for your help, I'll bring it to an apple store, but realy if they only propose me to replace the logic board (and if I can't repair the logic board myself), I'll be like "ok, I'll buy a 300$ computer, put the 8Go and SSD into it, and voilà"

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While symptoms can often lead us to a problem. The length of time the symptom is present can make diagnosing much harder.

I would recommend to get a set of schematics for the system and start by reviewing the power rails as I'm suspecting that is the issue here.

But before you start tracing, how about making a detailed inspection to make sure you don't see any burnt components or liquid spill damage.

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I didnt see any burnt components or liquid spill damage, I looked for like 1 hour but maybe I have miss something.

Concerning the schematic, is there a good website where I can find those ? Not sure if I'll be able to read them but in the worst case I'll learn :D

Thanks for your help

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@hmatthieu one other thing to look for are discolored traces Recently I had a logic board with slightly discolored trace that ended up being my problem. simply bearing the trace before and after the discolored area and soldering in a jumper did the trick . The traces are brown and will appear slightly lighter in color .Use a multi meter to test the area for continuity in the trace solder in jumpers to repair

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I'll try that too, I'll keep you in touch, thanks again for your advices.

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Matthieu Hocquart will be eternally grateful.
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