Apple iMac 27 inches Late 2013 - Display failure  - Page 1
Forum section: electronics / repair

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 27, 2022, 08:20:43 am
content: Hello all,This Mac has been working fine for many years then few weeks ago, its display progressively failed.Attached few pictures showing the symptoms where after checking on some website, top level analysis mentions the four green LED's internal status as a possible guide:LED 1: Indicates that the motherboard has detected the holding voltage from the power supply. This LED will remain on as long as the iMac is connected to the current. It will stay on even if your iMac is turned off or hibernated. It will only turn off the power or if the power supply is defective.LED 2: Indicates that the motherboard has detected the correct voltage from the power supply when the computer is turned on. This LED will stay on when the computer is too and the power supply is working properly.LED 3: Indicates that the computer and graphics card are communicating. This LED will stay on if the computer communicates correctly with the graphics card. If LEDs 1 and 2 are on and you hear the powering sound, but this LED is off, then the graphics card may not be installed properly or needs to be replaced.LED 4: Indicates that the computer and LCD screen are communicating. This LED will stay on if the computer is turned on and the video signal is generated. If the LED is on but the screen does not turn on, then the LCD screen or inverter may not be installed properly or need to be replaced.As you can see in the attached pictures, the four green LED's are lit. However if I disconnect say one cable amont the two linking the LCD display from the main board, only three LED's will lit.In the picture, initially you see a small blue verticals bands then say after 1 or 2 minutes, it will be wider and spread on other places of the screen.Do you think it is doable to repair, is it easy, is the root cause known ?Thank you in advance, Albert

author: PartialDischarge
author_rank: Super Contributor
timestamp: September 27, 2022, 08:35:10 am
content: Take it to a repair shop who do this kind of job on macs. I remember I had mine fail also and it was the graphics chip bga solder pads failing. Due to heat they fail it seems, so it just needs resoldering.

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 28, 2022, 05:41:58 am
content: Well this iMac was made late 2013 so more than 10 years, it will cost to bring to repair shop where the spirit of this forum is to self-repairI know with previous version back in 2009, 2010 and 2011 the issue you report (GPU ball soldering failure then baking to solve) but here, I'm wondering if the failure is not due to another reason.As a reminder, the main board 4 green LED's are all ON which includes LED #4 (Indicates that the computer and LCD screen are communicating. This LED will stay on if the computer is turned on and the video signal is generated. If the LED is on but the screen does not turn on, then the LCD screen or inverter may not be installed properly or need to be replaced.)Do you think this confirms the problem to be on the LCD electronics or still consider it could be the GPU failure ?Where is the inverter of the LCD screen ?Albert

author: kripton2035
author_rank: Super Contributor
timestamp: September 28, 2022, 06:29:46 am
content: this looks really like a GPU fail. you can try a reflow, but as always these reflows do not last very long some months at best.2011 imacs had almost all a GPU problem. the 2013 are different. not a lot of these failures happens on 2013 imacs.

author: Rasz
author_rank: Super Contributor
timestamp: September 28, 2022, 06:23:49 pm
content: So nice of Apple to not provide video in/out!> NVIDIA GeForce GT 755Mthose didnt fail like previous generations. This sure looks like broken LCD.

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 29, 2022, 10:04:47 am
content: Yes that is correct, these late 2013 iMacs (I've three of them) do have NVIDIA GeForce GT755M 1024Mo graphical processor unit which seems to run cooler.I do have mid-2010 and mid-2011 iMac (total of two) with respectively ATI Radeon HD5670 512Mo and AMD Radeon HD6970M 1024Mo graphical processor units, the last failed two times due to the BGA ball game.Now to go back to the Late 2013, see pictures again after say waiting 2 mins booting (phase 1, phase 2 and phase 3). I still do not understand whyPartialDischargeandkripton2035conclude the GPU fail (the GPU is on main logic board, not on display unit) because all green LED's are lit. Furthermore from my memory, when GPU fails on my older 2011 iMac then very quickly at boot no display or just plain display with question apple mark. Unless I'm wrong, the iMac seems to follow the different booting steps with final step of waiting for my username password.I attach another picture, we see both ribbon cable (one for video data I guess and the other for display power supply I guess), could one ribbon or its respective connector be failed ?Has any member on the forum deconstructed these LCD display to then check their internal electronics, are there a local inverter or power supply inside... any guidance much appreciated.Albert

author: kripton2035
author_rank: Super Contributor
timestamp: September 29, 2022, 11:34:37 am
content: the only way to know would be to test with a known working display module...it could be the display module, but I'd rather bet on the gpu (and so motherboard)

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 29, 2022, 12:53:39 pm
content: Quote from: kripton2035 on September 29, 2022, 11:34:37 amOne option I'm indeed considering would be to buy a used iMac late 2013 on eBay then try a known working LCD display module.However before going that road, I'm still wondering how do you interpret the LED's diagnostics from this websitehttps://fr.ifixit.com/Tutoriel/How+to+find+and+read+the+Diagnostic+LEDs/103545Please look at last step (etape 25) where in my case, the four LED's are ON. Is it possible to have a GPU to be failed but this is not detected neither reported by LED 3 and/or LED 4Merci, Albert

author: Rasz
author_rank: Super Contributor
timestamp: September 29, 2022, 01:37:57 pm
content: the leds wont tell you gpu is faulty if the fault is anything other than being completely deadtry disconnecting video data ribbons and see if the picture on lcd is still this mess even with no signal

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 29, 2022, 01:55:30 pm
content: Quote from: Rasz on September 29, 2022, 01:37:57 pmOk so I've just tried now these 2 tests.As a reminder, there are two ribbons: one which is clearly the LVDS video data and the other with 6 wires (3 black and 3 grey) which I believe is the power rail for the back LED of the display.When I only disconnect the small ribbon, all the 4 diagnostics LED will stay ON but we see nothing on the display.When I only disconnect the video ribbon, only 3 diagnostics LED stay ON, the fan will speed very strong and nothing on the display.

author: andy2000
author_rank: Frequent Contributor
timestamp: September 29, 2022, 02:49:50 pm
content: Why not connect an external monitor to one of the Thunderbolt ports? It won't be 100% conclusive if the external monitor works, since a GPU problem could affect only the internal display, but usually a bad GPU will affect both. If the external display doesn't work, then it has the be the GPU/motherboard.If you don't have access to a Displayport monitor, then buy a mini Displayport to HDMI adapter and connect it to your TV.

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 29, 2022, 04:07:08 pm
content: Quote from: andy2000 on September 29, 2022, 02:49:50 pmI do not have any TV but I do have two valid iMac 27 inches (same late 2013) which work. Do you know if is is possible to declare one valid iMac to become an external display of the failed one discussed here, if yes what method, what cable ?

author: Rasz
author_rank: Super Contributor
timestamp: September 29, 2022, 04:25:37 pm
content: wait, you have two more units and didnt even try opening a working one and substituting screens?

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 29, 2022, 04:33:29 pm
content: Quote from: Rasz on September 29, 2022, 04:25:37 pmYou're funnyOne unit is used in my bedroom for personal use with my wife, the other for my consulting company. Furthermore to remove the display from these iMac is not easy stuff (cut the glue around, risk of breaking the protective glass then install special stick glued bands...).If it was imac from 2009 or 2010 or 2011, easy because the display is magnet installed but from 2013 these iMac really suck.This is why either I find a method to use one of my valid iMac late 2013 as an external display or I buy a used working 4th iMac which i'd deconstruct its display.

author: kripton2035
author_rank: Super Contributor
timestamp: September 29, 2022, 09:29:38 pm
content: QuoteIIRC, only the 2011 27" imacs were capable of being used as a monitor. it was just some key combination at startup that did it. and you had to use the thunderbold cable.

author: kripton2035
author_rank: Super Contributor
timestamp: September 29, 2022, 09:32:28 pm
content: Quoteled4 tells you that the CPU is communicating with the GPU and back. it does not tell you if something is broken after the GPU. if you detach the lvds cable, the gpu detects it and tells the cpu not to lit the led4.still pretty sure the gpu is bad, after the other last tests. again you should test with the same display from another same imac...

author: AndyBeez
author_rank: Frequent Contributor
timestamp: September 29, 2022, 11:56:32 pm
content: Model number A****? Have you tried to track down the schematic for your iMac? Will probably cost around $£€10 for the boardview .brd file.

author: kripton2035
author_rank: Super Contributor
timestamp: September 30, 2022, 06:50:43 am
content: Quote from: AndyBeez on September 29, 2022, 11:56:32 pmhttps://www.badcaps.net/forum/showthread.php?t=79140

author: Tantratron
author_rank: Frequent Contributor
timestamp: October 01, 2022, 07:55:05 am
content: Quote from: AndyBeez on September 29, 2022, 11:56:32 pmWell the model is A1419 but this means slim model through different years, mine is late 2013.Quote from: kripton2035 on September 29, 2022, 09:32:28 pmOk so it seems the quickest route for this diagnosis and/or repair is that really I try to eBay found cheap same model with working GPU, display then remove glued display to swap sub-systems.One option would be that I remove the glued display from the one I use in my company since it works with HDD and I plan to replace with SDD to get more speed.By the way, speaking of HDD => SSD on late 2011 iMac or mid-2010 iMac which I still have. Clearly the speed becomes ballistic but the late-2011 got again GPU failure two times after replacing new GPU's. However the mid-2010 still works, no failure but I wonder if sometimes super-increasing CPU speed when going with SSD could not heat over-load or stress the GPU's previous generation. The CPU runs much faster due to fast bus access thanks to SSD read-write timing but maybe this can exhaust the GPU not used to go so fast !Anyway let's wait I find a spare late-2013 display with LVDS cable to declare what is wrong with mine.

author: kripton2035
author_rank: Super Contributor
timestamp: October 01, 2022, 09:07:59 am
content: really a very few gpu problems on 2010 imacs. and almost all 2011 models died from that !you can find compatible video cards on ebay, with some tweaking you can make them work on a 2011 imacsometimes, I had issues on one or two imacs that never accepted these new video cards.this seller has all the cards you need, already bought some from him, very kind and responsive.https://www.ebay.com/str/taishan1980the ssd will not kill your gpu card. and frankly I cannot use anymore any computer without ssd...

author: kripton2035
author_rank: Super Contributor
timestamp: October 01, 2022, 09:12:12 am
content: anyway the best move actually is to open another imac to install the ssd, and use it to test the defective imac with display or video cardedit: oups sorry my bad... forgot these 2013 imacs have the gpu on the motherboard... sorry forget my message above !

author: Tantratron
author_rank: Frequent Contributor
timestamp: October 06, 2023, 04:28:18 pm
content: Quote from: Rasz on September 28, 2022, 06:23:49 pmHello, it has been one year after I started this thread and here is an update.For the last 6 months, I've started to have some partial and minor failures with my other iMac27 " (late 2013) due to SSD starting to have problems (verified later thanks to DriveDX application). This iMac was bought to eBay in Germany to a guy that installed supposedly a new SSD, the brand being SANDISK.So I've decided to buy a reconditioned iMac from Apple (model 2020) last week then I've deconstructed the late 2013 which works (CPU, Display except partial failure of SSD). That way I was able to swap the working display into my other iMac (late 2013) which is failed (purpose of this thread).The conclusion was quick: now the LCD display works fine when connected to the old motherboard so the problem was not GCPU related.Does anybody know if it is easy or worth to repair a failed display 27" for iMac late 2013 or what sub-part are worth to keep as donator ?

author: Tantratron
author_rank: Frequent Contributor
timestamp: October 24, 2023, 03:49:02 am
content: Now it is proven the LCD is broken, does anybody knows if it is easy or worthwhile to repair this display showing issues as shown in the attached pictures ?Another question about re-installing a LCD on the iMac metal main frame. Once the LCD was removed thanks to plastic pizza cut style too to cut the internal adhesive. Then re-installing another LCD consist to add new adhesive glued ribbon which will seal everything.However do you know if it is OK to rather scotch tape all around the LCD glass to the slim main frame ?Even if it is not too esthetic, it could help removing later the LCD for whatever maintenance or change HDD or SSD inside ?Any thermal or sealing issue with this method or do you recommend to rather use the double glued ribbons ?Thanks in advance, Albert

author: kripton2035
author_rank: Super Contributor
timestamp: October 24, 2023, 06:22:41 am
content: I've many times scotched painter tape outside the imac to hold the lcd during tests.it works although it will not hold up for a long time, and it's really hideous...