Screen is not working (external display working)

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iMac Intel 21.5" EMC 2389 Mid 2010

Model A1311 / Mid 2010 / 3.06 & 3.2 GHz Core i3 or 3.6 GHz Core i5 Processor

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Alex Hus @alexhus

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Publié: 2 févr. 2016

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Screen is not working (external display working)

Hi

I have an iMac that i do not know the full history of (brought from a sale sold as seen)

When i got the iMac home connected it powered up but it will not display anything

But when it is connected to an external display though mini display port i can get an image

diagnostic led 1,2,3 are on but 4 is off

my main questions are:

Can i test the display?

Is there away to fix it ?

Is it worth spending £100 on a screen?

Or is it simply the display data cable (from the display removal guide it seems common)?

I have checked all connections

(vertical sync cable,LED backlight power cable, display data cable, LCD thermal sensor)

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oldturkey03 @oldturkey03

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Publié: 2 févr. 2016

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lexie huseyin,

LED #4

• Indicates that computer and LCD panel are communicating. This LED will be ON when

computer is turned on and video signal is being generated. If LED#4 is ON and there is no

image on display, then the LCD panel, the LED backlight board, or the cables between LCD

and logic board or backlight board might be installed incorrectly, or need replacement.

If fourth LED is not visible after power on:

• Verify internal DisplayPort cable connections between LCD panel and logic board

• Inspect LCD display cables for cable damage

• Verify external video functionality, and according to result check the following items:

If external display works then verify/replace the LED backlight board

If external display works then verify/replace the LCD panel

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

Since your iMac detects an external display, the Video circuitry on your logic board functional. Inspect DisplayPort cable to back of panel connection. Reseat and test again. If you still have trouble, I would focus on the backlight board. Shine a flashlight at an angle against the screen in a darkened room and see if you can make out any shades/shadows. If so I'd replace the backlight board before the panel.

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Personally I would check for cold solder joints on the Display driver board: iMac Intel 21.5" EMC 2389 LED Driver Board Replacement

2 févr. 2016 par mayer

hi oldturkey3

Thanks for the response

i just checked

the thermal sensor wires are damaged (i think will not affect display?)

the display data cable looks slightly "meh" but i do not think is bad

i did the back light test and got nothing

so i think it is either the display data cable or lcd panel

just looked on eBay

used screen all connectors £60 (working

display data cable £20

so for extra £40 i can get screen but if its just the display cable then thats £40 wasted

thanks again!!

2 févr. 2016 par Alex Hus

hi mayer

thanks for the response

how would i check the cold solder joints

just visually?

and what would i be looking for?

thanks

2 févr. 2016 par Alex Hus

I'd still start with the backlight board. Just a hunch....:-)

2 févr. 2016 par oldturkey03

I had/ have that hunch to but i have looked in different lighting with different flashlights I'm struggling to believe it

but as a mechanic you can have a sound from a car that sounds terminal and it will just be something simple and stupid so i also have that doubt

can the backlight board be tested with a multimeter ?

i am going to be looking over it all again tomorrow just to be 100%

if it doesn't work i will most likely but the screen and cables

thanks again

2 févr. 2016 par Alex Hus

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Personally I would check for cold solder joints on the Display driver board: iMac Intel 21.5" EMC 2389 LED Driver Board Replacement — mayer
hi oldturkey3

Thanks for the response

i just checked

the thermal sensor wires are damaged (i think will not affect display?)

the display data cable looks slightly "meh" but i do not think is bad

i did the back light test and got nothing

so i think it is either the display data cable or lcd panel

just looked on eBay

used screen all connectors £60 (working

display data cable £20

so for extra £40 i can get screen but if its just the display cable then thats £40 wasted

thanks again!! — Alex Hus
hi mayer

thanks for the response

how would i check the cold solder joints

just visually?

and what would i be looking for?

thanks — Alex Hus
I'd still start with the backlight board. Just a hunch....:-) — oldturkey03
I had/ have that hunch to but i have looked in different lighting with different flashlights I'm struggling to believe it

but as a mechanic you can have a sound from a car that sounds terminal and it will just be something simple and stupid so i also have that doubt

can the backlight board be tested with a multimeter ?

i am going to be looking over it all again tomorrow just to be 100%

if it doesn't work i will most likely but the screen and cables

thanks again — Alex Hus