iMac late 2013 - how to perform Apple Diagnostics with external monitor? Screen dead

[ewido]

Hi there
I have an iMac 27" late 2013. Wonderful machine.
My screen have gone black and with flickering blue and yellow lines both horizontal and vertical.
It is possible for me to use the computer with an external monitor. Everything works except the screen on the iMac.

I want to perform an Apple Hardware Test/Apple Diagnostic on the iMac. But is it possible with a external monitor?
To perform the Apple Diagnostic turn off your computer, remove everything else than power chord, mouse and keyboard. Turn the computer on and right after press and hold "D". You have to be quick.

Do you know what's wrong with my computer?

How I see it:
The graphics card are ok - since everything works with an external monitor.
The backlit/screen light works - since I still can adjust the backlight.
The harddrive works - since everything other than the screen is working.
I have installed all the newest updates.
The display itself is all good. It's the signal that is wrong.

My guess is:
- it's either a loose video cable connection.
- some kind of problem with the screen dedicated powerunit/card - if it have one. Don't know.

I hope you can help.
Regards

 

[chscag]

Welcome to our forums.

It's possible your machine has a loose video cable. Go to www.ifixit.com and look up the instructions for removing the display from the machine so you can check the cables and connections. Be very careful when doing so and be sure to order the kit that has the glue strips to put your iMac back together. If you think you do not have the necessary skills to do the work, take the machine to an Apple Store or an authorized Apple service dealer and have them do it.

BTW, the Apple Hardware Test is not the best. Only the diagnostics used by Apple Technicians is really of any value.

 

[ewido]

Thanks for the quick reply Very helpful.
I have consulted the local computer repair shop by e-mail.
They say it needs a new display and the price will be 1.050,- dollars (this is in Denmark/Scandinavia). That's kinda pricey.
So I will try to search ifixit for the loose cable issue first.
If it doesn't work I'll try to install a new display myself. It seems doable. If I can get my hands on one, that is.

 

[pigoo3]

They say it needs a new display and the price will be 1.050,- dollars (this is in Denmark/Scandinavia). That's kinda pricey.

Yes...these sort of major replacement parts can be pretty expensive. At Powerbookmedic.com...they sell a replacement display for between $499 & $649 USD (none in stock at the moment):

https://www.powerbookmedic.com/Intel-iMac-27-Late-2013-Display-p-79821.html

You could also check eBay. This at least gets you a starting place on prices if you decide to do the replacement yourself.

ifixit.com is a great place for the DIY replacement procedure...and well as videos on You Tube.

- Nick

 

[chscag]

Thanks for the quick reply Very helpful.
I have consulted the local computer repair shop by e-mail.
They say it needs a new display and the price will be 1.050,- dollars (this is in Denmark/Scandinavia). That's kinda pricey.
So I will try to search ifixit for the loose cable issue first.
If it doesn't work I'll try to install a new display myself. It seems doable. If I can get my hands on one, that is.

By all means, check for the loose cable first. I'm a little taken back by a repair shop who diagnosed your iMac by email and said it needed a new display. That sounds more like they're trying to get you to spend $$ on repairs.

And as Nick has advised you, if you do indeed need a new display you can probably get one on eBay or locally. Be careful when dealing with eBay. Also take into account that a display for a 27" iMac is large and heavy.

 

[ewido]

Thanks for the advice

I have made a video of my new beautiful "screen saver". Maybe it can help others with the same problem.

https://www.youtube.com/watch?v=9wXLS5V-8C8

 

[chscag]

That YouTube video explains the visual problem. It does appear to be a cable problem but you won't know for sure until you open up the iMac and check it out yourself. It does not appear to be a defective display but one never knows....

 

[ewido]

Hi, thanks.
I also think it must be a connection problem. All the pixels work fine. I seems like it just have problems handling the signal.
I just talked to my local tech repair shop.
They offer to do a free check to figure out the problem.
So I'll get them to take a look at it. Hopefully it's a loose cable or something easy. Then if it turns out it really needs a new LCD, I'll do it myself. I have found a new replacement LCD including glass for 560 dollars on Ebay. And since it comes with the glass I'll save the work of mounting this also.

 

[chscag]

Sounds like a good plan. By the way, in case you don't already know it, the display is glued to the glass so they both have to be replaced together.

 

[ewido]

Hi, so it's not possible to just buy a new LCD and re-use the glass from my iMac? Isn't it just glued in with rubber adhesive tape?
Thanks

 

[chscag]

No, it's not possible. Any attempt to remove the glass will destroy the LCD. Apple in their "wisdom" have engineered it that way. All Apple displays are now firmly adhered to the glass and must be replaced as one unit. Also I don't believe you can buy an iMac display for the 2012 iMacs and later that is not glued to the glass.

The adhesive tape you mention is used to adhere the LCD-Glass assembly to the iMac chassis. But again, the glass and LCD must be replaced as one unit.

 

[ewido]

Very interesting, thanks!
I've found this one which should work. Hopefully.

http://www.ebay.ie/itm/NEW-LCD-DISPLAY-PANEL-GLASS-COVER-Apple-iMac-27-A1419-Late-2012-Late-2013-/272657402996?hash=item3f7ba5cc74:g:2jkAAOSww9xZCyq3