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Model A1419 / Ende 2013 / 3,2 und 3,4 GHz Core i5 oder 3,5 GHz Core i7 Prozessor, ID iMac14,2

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Logic board or Power Supply faulty?

Hi All,

Currently my iMac late 2013 screen is totally blacked out. I pulled the LCD off and notice only LED1 in logic board is blinking in addition the fan is not running,

How can I know what needs repair is it with logic board or power supply (PSU)?

Here’s a video with my details: https://www.youtube.com/watch?v=6zlAKCEJ...

Any advise would be appreciated.

Beantwortet! Antwort anzeigen Ich habe das gleiche Problem

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@h4r1y0n0

make sure you check the power button etc. as well. the how to is included in the deep dive.

Diagnostic LEDs (A)

LED 1

Indicates that the trickle voltage from the power supply has been detected by the main logic board. This LED will turn on when you connect the iMac to a working AC power source. The LED will remain on as long as the computer is on or asleep.

When the computer has been shut down correctly, LED 1 behavior may differ:

If a startup event is scheduled in System Preferences/Energy Saver, LED 1 will stay on after a correct shutdown.

If no startup event is scheduled in System Preferences/Energy Saver, LED 1 will turn off and will stay off as long as the power cord is kept connected and an AC power source is present. Disconnecting the power cord and plugging it back in will turn this LED back on, even if the computer is still off.

After disconnecting and reconnecting the AC power source, this LED could remain off:

If the AC power source is missing or disconnected.

If the logic board is disconnected from the power supply or the AC receptacle.

If the power supply board is faulty.

LED 2

Indicates that the computer is turned on. This LED will be on as long as the computer is turned on (but is not asleep) and the power supply and voltage regulators are working correctly.

If no LED is visible:

Disconnect the power cord from the computer and wait 15 seconds to reset the power supply and LED status.

Reconnect the power cord and check the LED status again.

Verify the AC source.

Verify that a known-good power cord is connected.

Verify the cable connection between the AC inlet and the power supply.

Verify the cable connection between the power supply and the logic board.

Verify the power supply.

LED 1 + LED 2 = Power is available and the system is turned on.

If the second LED is not visible when the power button is pressed:

Verify that the power button is connected to the power supply.

Verify power button functionality.

Verify the cable connection between the power supply and the logic board.

Verify the power supply.

Verify the logic board.

Check the power supply temp sensor area as well as try the reset test pads by shortening out across the solder pads with a screwdriver or similar (bottom right on the board)

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Following the deep dive troublshooting. At step 12 you can make determination if it is a power supply issue or the logic board (my money is on the power supply)

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Update (08/07/2019)

Here is the location of the reset pads (C)

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pleasedontfront

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I'm trying to do the forced RTC reset in step 19 of the deep dive but can't locate the reset pads. Do you have the actual manual that provides a link to the location of the pads?

von

Ah ok thanks. I was trying to find the location of the pads for an iMac 21.5" Late 2013: ME087LL/A (2.9 GHz Core i5). The schematic you posted above appears to be a different board. Step #18 in the deep dive indicated a link to the late 2013 board. I've tried pulling the coin battery out to force the reset but that hasn't yielded results. Still only got the first LED turning on..

von

pleasedontfront what 820-XXXX number is your board?

von

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You stated in the vid you replaced the power supply with one you bought on eBay. Its possible its bad, its also possible the logic board has a problem.

Before you replaced the power supply what was the onboard diagnostic LED’s telling you the same or different than what you have now?

Also did you try to measure the voltages of the power supply?

Lastly, what the system powered through a surge suppressor or UPS? Often power surges or lightning will damage one or both the power supply and the power logic on the logic board.

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Before you replaced the power supply what was the onboard diagnostic LED’s telling you the same or different than what you have now?

Comment : same.

Also did you try to measure the voltages of the power supply?

Comment : how to measure?

Lastly, what the system powered through a surge suppressor or UPS? Often power surges or lightning will damage one or both the power supply and the power logic on the logic board.

Comment : I’m stay in SG hence we don’t really use UPS or Surge since the electricity in here are quite stable.

von

The power surge risk is not always caused by your power company. In your case living in Singapore you have a higher risk of lightning! Did you know Singapore is known as the ‘lightning capital’? Which is why a Surge suppressor is needed or better yet a UPS.

von

Sadly it's looking like your power regulation logic on the logic board is damaged. I don't have a system available to take measurements from to guide you. Apple changed the design enough with the newer 'Thin Series' and they have a few different units now as well.

von

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Hi guys,

I have some experience to share.

It turns out that the first time i opened it up and exchanged the PCI-E drive the imac didn't boot.

The only thing that happened was that the status LED #1 on the main board were not functioning as it should.

I'm sharing this because i found no solution online for my problem but i managed to solve it.

There are 4 LED diagnostic lights on this board, and the first (the one on the bottom) should indicate if there is AC power present on the power supply block. Normally if you have AC connected, the led should be lit, otherwise off. Mine was blinking and the supply was making subtle but weird noises.

After 1 hour of trying all the things that i could online find after reading about people that exchanged the power supply thinking it was faulty but not solving the problem, i removed all the ram sticks leaving one that i was sure it worked and replaced the nvme 660p drive and adapter for the original 128Gb drive.

It booted up.

Turns out it was my NGFF adapter that came faulty as i ordered another one and now i'm writing off from my "refurbished" machine.

If you see the AC LED blinking don't stress yourself. Try going back to the original drive and see if it comes back alive. Most probably you have a faulty NGFF adapter.


Hope i can help anyone saving some money.

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Did you ever find an answer? I have no diagnostic lights, already changed the powersupply and tested the voltages to be good at the MB power supply header. Leary about swapping the MB on such an old system, maybe just sell it for parts?

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Honglim Yang wird auf ewig dankbar sein.
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