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A1418 / EMC 2833 / Late 2015 / 3.1 GHz Core i5 or 3.3GHz Core i7 Processor. Released October 13, 2015.

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Purple Hue on the edge of the Screen after SSD UPGRADE

Hi iFixit,

I recently replaced my hard drive with an SSD using this bundle: iMac Intel 21.5" Retina 4K Display Hard Drive Replacement

The speed works great and the repair was easy. But I noticed that there’s a purple/purple hue on the left and right side of the screen.

Do you know what the reason for this might be ? I want to order more adhesive and fix it up, but I’d like to know if you have any ideas before I start.

Thanks,

Rama

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@rama_watts - Did you use the special adhesive cutter that comes in the adhesive strips kit?

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Yes, and I also made sure not to push the card in more than 3/8"

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@rama_watts - Double check to make sure the internal display is the issue. Plug in an external display does it come up clean?

The newer iMac's 2012 and newer use a different video dialog (iDP also known as eDP vs the older LVDS). Think it like the difference between analog vs digital TV the over the air signal often has ghosting and other artifacts unlike the newer digital signal. The only area which makes sense here is either an issue within the displays T-CON board or the main logic board.

Isolating which using an external display is the only way I know how to figure this out.

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@danj Hi Dan,

Sorry for such a late reply. I've plugged in an external display and the external display does not show any purple hue on the edges. Any suggestions?

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@rama_watts - Sorry my original answer applies here - Time for a new display.

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OMG, you have the dreaded Hendrix, "Purple Haze" problem, RUN it may be contagious.

https://www.youtube.com/watch?v=cJunCsrh...

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@mayer - A more current Purple reference would have been Prince - Purple Rain the vid has lots of purple haze! ;-}

I don't know of many people who ever heard Hendrix who I love! We're both showing our age ;-{

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Purple hue generally points towards a signal problem. Check the video connector for loose/damaged connection between the LCD and main logic board. Be sure to check both ends. Hopefully a simple reconnect will fix this.

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How do I check the video connector? Do I have to open up the Mac again?

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Hi Rama

The video connector for iMacs is generally a 30-pin wide gold plated connector coming from the back of the screen to the main logic board. You'll want to check for bent pins on the cable and damage to the connector on the board. Making adjustments to this cable could fix your issue if there is no physical damage to the LCD panel/Screen Assembly itself.

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@refurbpro - LVDS signaling was used in the older iMac's (2011 and older). When Apple went with the thinner iMac's they switched to iDP (eDP) signaling which is like the difference between analog TV Vs digital TV.

The haze issue you might encounter within LVDS connections just doesn't happen here with iDP.

Here's a good source of display defects Sony T-CON training manual as well as iDP (Internal DisplayPort) Technology Overview & DisplayPort

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@danj I really appreciate the info! I can only suggest solutions that have worked for me in the past, but I'm always willing to take a deeper look.

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@refurbpro - Most haze issues I've seen on the newer models tend to be either image persistence issues or pressure marks from the act of taking the display off around the edge areas. Both issues can be fixed by new screens.

Seeing a picture or two would help in ID'ing which was the cause.

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@rama_watts Sadly, you’ve isolated the issue down to the display. Some how you managed to damage it in the process of taking it off.

You’ll need to replace it if you can’t live with the haze effect. Here’s the needed part iMac 21.5" LCD Display Panel - Retina 4K (used) P/N 661-02990

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@rama_watts “there’s a purple/purple hue on the left and right side of the screen.”Blue/Purple hue issues are actually most commonly caused by LED backlight issues. Sure, a new display panel will fix the issue since the backlight is part off it, but you wanted to “know what the reason for this might be ?

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@oldturkey03 - I've never seen the LED's alter their color other than yellowing from burning the reflector plastic.

Can you expand how the backlight LED's alter their color here into the Blue spectrum, The only thing I can think of would be the driver voltage being too high not the backlight in the display its self. Yet I've not seen this in all of the systems I've fixed.

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@danj that is absolutely great to hear. I am so thankful you never had to deal with that. Outstanding.

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@oldturkey03 - I was serious! Can you expand what was the issue.

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@danj let me try to explain this in my simple minded ways. As we all know LEDs’ do not directly produce white light. There are two ways in which white light is produced from LEDs’ . One (most common) is using a blue LED with a phosphor coating to convert blue light to white light by a process called fluorescence. The other method is by using RGB LEDs’ to produce white light. White light is produced by varying the intensities of the individual red, blue and green chips. The vast majority of LED lighting  are of the PC (phosphor coated) package type. It is known that LEDs’ phosphor coating method will, with aging, demonstrate curling of the phosphor relative to the LED chip. It is this curling that cause a spectral shift toward blue.  Another coating method is known to cause a shift toward yellow as high temperatures cause air gaps to open up between the phosphor coating and the LED chip, which is called delamination.

 A major part of the challenge is due to the LEDs’ sensitivity to temperature changes. The chips naturally run hot, and without adequate temperature control, overheating occurs and performance will rapidly degrade. Yes, newer LED packages have modified the earlier PC method to address the ‘curling’ and ‘delamination', yet color shift will still occur as a result of factors such as age, overheating etc.

So, I am never surprised to see that a LCD panel eventually shows a blue/purple or yellowish tint. But that is just me so I am really glad to hear that you never encountered this.

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