All of the 4 Logic Board lights are green but screen does not turn on.

Question

iMac Intel 21.5" EMC 2428

Model A1311 / Mid 2011 / 2.5 & 2.7 GHz Core i5 or 2.8 GHz Core i7 Processor

432 个问题查看全部

Mr_T @mrt100

声誉积分: 1

1

发帖于: 2021年3月22日

更多选项

All of the 4 Logic Board lights are green but screen does not turn on.

Hi, I wonder if you can help me.

I have a iMac 2011 21.5" and I have recently replaced the thermal paste on the CPU & GPU as it needed to be replaced.

All of the cables are attached properly as the 4 LED lights on the logic board are green when the iMac powers on.

The only problem is the screen is black and even when the computer chimes the screen never turns on, BUT the 4th LED on the logic board is green indicating the screen is connected properly.

What can I do? What does it mean?

Thanks

Here is my GPU I can see a tiny amount of thermal paste in-between some of the SMD devises. Does it need to be isopropyl alcohol to clean effectively the GPU as don’t have that in stock?.

回答此问题我也有这个问题

这是一个好问题吗？

是否

得分 0

7条评论

The little paste that dribbled can easily get cleaned up. You'll need to carefully clean the GPU chip of its paste and being careful not to touch the gapping paste or best yet I would clean it off and replace it with thermal pads. The gapping paste is not as good as the the pads.

I'm more concerned on when you apply the fresh paste you don't over do it.

由 Dan 完成的 2021年3月23日

Hi Dan, I have put new thermal paste on the GPU making sure I didn't over do it and still a black screen.

由 Mr_T 完成的 2021年3月24日

Sadly, its looking like your GPU board has failed.

由 Dan 完成的 2021年3月24日

Oh no, I have had the iMac powered on for 2 hours and the heat pipe is warm that connects to the GPU I don't know if it shows it's still working? It's a bit strange that the GPU has died when I opened the iMac, what might have caused that?

由 Mr_T 完成的 2021年3月24日

ESD is one possibility. In the winter early spring the air is quite dry in the northern hemisphere with the cold.

You could have damages something in the process. It's also possible just kismet.

由 Dan 完成的 2021年3月24日

显示更多的2条评论

添加一条评论

1个答案

The little paste that dribbled can easily get cleaned up. You'll need to carefully clean the GPU chip of its paste and being careful not to touch the gapping paste or best yet I would clean it off and replace it with thermal pads. The gapping paste is not as good as the the pads.

I'm more concerned on when you apply the fresh paste you don't over do it. — Dan
Hi Dan, I have put new thermal paste on the GPU making sure I didn't over do it and still a black screen. — Mr_T
Oh no, I have had the iMac powered on for 2 hours and the heat pipe is warm that connects to the GPU I don't know if it shows it's still working? It's a bit strange that the GPU has died when I opened the iMac, what might have caused that? — Mr_T
ESD is one possibility. In the winter early spring the air is quite dry in the northern hemisphere with the cold.

You could have damages something in the process. It's also possible just kismet. — Dan

Dan @danj 声誉积分: 480.1千 Self employed contract worker 35 329 971 · Answer 1 · 2021-03-22T12:25:50-07:00

最有帮助的答案

Dan @danj

声誉积分: 480.1千

Self employed contract worker

35

329

971

发帖于: 2021年3月22日

更多选项

What happens when you shine a flashlight into the screen?

Place the flashlight on the glass at a sharp angle, you should see the faint image of your desktop and its icons. If you do they your backlight logic need repairs which is why your onboard diagnostic LED's are all lit as the backlight is not monitored by the onboard diagnostics.

You’ll need to open the system up and pull the GPU board off to clean the thermal paste off.

You’ve either over done the paste so now the SMD devices on the chip carrier has paste on them or you have a bad board.

I’ve marked a few of the small SMD devices that often get covered with TIM which can cause issues.

这个答案有帮助吗？

是否

得分 2

8条评论:

Hi Dan,

Thanks for your response, I have tried using a flashlight at a sharp angle and still nothing. I have heard online it might be the LVDS cable port or the screen but I was so careful on opening the screen as I have repaired another iMac before. What do you think?

Thanks

由 Mr_T 完成的 2021年3月22日

@mrt100 - Lets check a few more things before we make that jump.

What does an external display show using a mDP or TB connection?

由 Dan 完成的 2021年3月22日

@danj - I have tried connecting it using thunderbolt but it said "no signal".

由 Mr_T 完成的 2021年3月22日

Then you know there issue is not the LVDS cable or the connector!

由 Dan 完成的 2021年3月22日

Oh yes your right! Thanks Dan, I'll try that out, does SMD devises mean the different components on the Logic board? Would I need to replace the thermal pads on the GPU as well as what I did last time was to try and reshape the original thermal pads on the chips?

由 Mr_T 完成的 2021年3月22日

显示更多的3条评论

添加一条评论

iMac Intel 21.5" EMC 2428

All of the 4 Logic Board lights are green but screen does not turn on.

Update (03/23/2021)

1个答案

Update (03/22/2021)

添加你的答案