iMac A1418 Black Screen 3 led On but 1 Off

Question

iMac Intel 21.5" EMC 2544

Model A1418 / Late 2012 / 2.7 & 2.9 GHz Core i5 or 3.1 GHz Core i7 Processor

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Piotr @suprnowa

Rep: 23

1

Postado: 3 de set de 2018

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iMac A1418 Black Screen 3 led On but 1 Off

Hello

After changing the disk on the SSD, a gray vertical bar appeared on my screen.After the next opening I had a few colored vertical stripes on the screen.I opened it again and I drank the tape on the power and plugged in. Now the screen is black. Make it start (dong ) there is a fan but no image. On the main board only 3 LEDs are light but the last 4 Led is off. Where do you look for a problem?

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@suprnowa what exactly do you mean by this "I drank the tape on the power "? Did you recheck your data dispaly cable? Check that and the connector for any damage.

3 de set de 2018 por oldturkey03

Yes i unplug my data display cable on power

3 de set de 2018 por Piotr

So i connect external video whit thundrbold-hdmi and work fine.

I have a picture on the external display. The only thing I noticed Mac is running very slowly. I have to change LCD Panel?

5 de set de 2018 por Piotr

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oldturkey03 @oldturkey03

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Postado: 3 de set de 2018

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@suprnowa start with this

LED 1 + LED 2 + LED 3 + LED 4 = Power is available, the system is turned on, the logic board is communicating with the GPU, and the internal LCD was found.

If the fourth LED is not visible after the system is turned on:

Verify the internal DisplayPort cable (eDP) connections between the LCD panel and the logic board.

Inspect the LCD display cables for cable damage.

Verify external video functionality and proceed according to the result:

If an external display works, verify/replace the LCD panel.

If an external display does not work, verify/replace the logic board

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Hi, I have a friend with a 2013 21" iMac (A1418 EMC 2638), the symptoms are similar to the OP's.

I hear the start up chime, I hear the fan turn on, I see some thin purple lines and thicker black ones that come on through the LCD in the middle of the screen.

I looked with a flashlight and do not see any icons or other indications that the screen is just really black.

All four diagnostic LED's are on which I understand is good. The one problem that concerns me is that when I plug in a Thunderbolt adapter to HDMI cable, I do not get anything on my TV. When I plug in the HDMI cable, the "source" on the TV indicates that there is a signal coming from the iMac but nothing ever shows up.

Based on all four of the diagnostic LED's being lit up, I'd think it was a bad LCD but the fact that nothing shows up on the secondary monitor, I'm unsure.

Any guidance would be greatly appreciated!

3 de jun de 2019 por Tony LaMarca

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@suprnowa what exactly do you mean by this "I drank the tape on the power "? Did you recheck your data dispaly cable? Check that and the connector for any damage. — oldturkey03
So i connect external video whit thundrbold-hdmi and work fine.

I have a picture on the external display. The only thing I noticed Mac is running very slowly. I have to change LCD Panel? — Piotr
Hi, I have a friend with a 2013 21" iMac (A1418 EMC 2638), the symptoms are similar to the OP's.

I hear the start up chime, I hear the fan turn on, I see some thin purple lines and thicker black ones that come on through the LCD in the middle of the screen.

I looked with a flashlight and do not see any icons or other indications that the screen is just really black.

All four diagnostic LED's are on which I understand is good. The one problem that concerns me is that when I plug in a Thunderbolt adapter to HDMI cable, I do not get anything on my TV. When I plug in the HDMI cable, the "source" on the TV indicates that there is a signal coming from the iMac but nothing ever shows up.

Based on all four of the diagnostic LED's being lit up, I'd think it was a bad LCD but the fact that nothing shows up on the secondary monitor, I'm unsure.

Any guidance would be greatly appreciated! — Tony LaMarca

Piotr @suprnowa Rep: 23 1 · Answer 1 · 2018-09-06T12:44:20-07:00

Piotr @suprnowa

Rep: 23

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Postado: 6 de set de 2018

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So i have one question.

If there is an image on the external monitor, the system works very slowly. The LCD Panel could have broken down so that it is black and does not illuminate and display nothing? Did something else on the motherboard get worse from the power / control LCD Panel?

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Jack C @jackc78141 Rep: 1 · Answer 2 · 2020-11-27T08:45:08-07:00

Jack C @jackc78141

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Postado: 27 de nov de 2020

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OK. A1418 2017

Lcd not powering or detected.

External monitor works fine albeit slowly.

You would think….its iMac the screen…right?!

Well the screen works perfectly on another identical iMac.

So screen ok, gpu ok…. but signal or power from imac to its own scrern., not working. Could it be a power to screen problem? Logicboard

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iMac Intel 21.5" EMC 2544

iMac A1418 Black Screen 3 led On but 1 Off

Update (09/03/2018)

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