iMac 2012 - black-and-white stripes, graphics lags, artifacts...

angniempol

macrumors newbie
Original poster
Oct 27, 2017
5
0
Dear Apple Users,

I bought a used iMac, late 2012, NVIDIA GeForce GT 640M, I5-3335S ?, 8 GB RAM, 1600 MHZ, PC3-12800, 1TB HDD. Everything was fine for two weeks until I turned the machine off for a night and when I came back to my office in the morning and started it, this happened:



https://goo.gl/jatMeD (https://we.tl/SMLBB1KKcK)


The first thing I did I called Apple Support and the guy asked me to perform different tests, including plugging my iMac out of the socket and, after several minutes, plugging it again. Nothing worked and I ended up installing High Sierra. This, however, did not work either. So, I took the machine and went to a certified technician who launched the iMac and, to my 'dismay', everything was fine! No artifacts, no lags, no black-and-white stripes on the screen. He told me he would perform some tests which took him about 15 minutes. After that I took my iMac back to my office, plugged it in back to the same socket - everything was OK.... for several minutes. Then, I thought - OK, maybe something's wrong with the socket itself and plugged the machine to a different socket. In this 'configuration' everything was all right for several hours. The device was in use until 9 pm when I put it to 'sleep' mode and went home. In the morning, when I came back, I woke my iMac up and, again, everything was fine. So, I left it for two hours because I was busy with a customer. When I returned and woke the machine up, the artifacts and black-and-white stripes appeared again. This time it wasn't even possible to browse a table in Excel or Google Docs - everything inside the document went white, including the tables. I tried plugging it in to a totally different power supply system in the other part of the tenement house I rent for my office (two different owners, two different systems) but the problem persisted. In despair, I took my iMac to a different certified technician - this time, a trusted one who had helped me several times few years ago. I called him yesterday evening and he said they had been performing graphic card 'endurance' performance tests and no artifacts showed up... But they promised to test my iMac further. I called them today at noon and the technician said the graphic card tests showed no negative results but he had performed a different test in which a graphic lag appeared just once - tabs in Safari and Chrome went 'plain' (meaning no X sign was visible) and they were flickering - just like in the video attached above (when logging in). But this happened only once. I asked him whether they had unplugged the machine for the night and the technician confirmed. And this wasn't my modus operandi when the graphics lags appeared. So, I suggested him not to unplug it and keep testing the device. We'll see tomorrow what comes up. In the meantime, I would be grateful for any suggestions which I could share with my technician to help us solve the problem...
 

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komatsu

macrumors 6502
Sep 19, 2010
472
34
You've been sold a pup I'm afraid.

It is possible, that 2 weeks ago, the seller or someone acting on behalf of the seller got a hot-air gun and gave your GPU chip a little warm up. This can mask a failing GPU problem for a short while until it flakes out again.

Not a lot can be done in a case like this unless you want to blow a couple of hundred $ on it.
 
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bbnck

macrumors 6502a
Mar 19, 2009
565
303
What part of the world do you live in? Depending on where you live and how the condition of the iMac was described, you may have the right to return it - but with any second-hand item, your rights are pretty non-existent in most countries except in cases where a seller has not been honest about the state or condition of the item.

I can only speak with a little confidence about how contract law works here in the UK, but the basic principle is anyone selling a used item cannot mislead someone by falsifying or withholding information on the condition of the item that would cause a reasonable person to be misled into buying it under a false pretence.
 
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alien3dx

macrumors 6502a
Feb 12, 2017
817
175
seem graphic card getting failure.. i'm not sure how mac replace graphic card thou
 

angniempol

macrumors newbie
Original poster
Oct 27, 2017
5
0
I live in Poland and consumer rights are pretty dodgy here in terms of second-hand items... So, what should I do now?
 

angniempol

macrumors newbie
Original poster
Oct 27, 2017
5
0
Guys, any idea how we could check whether it's HDD or a graphic card?
 

Razzerman

macrumors 6502
Sep 11, 2007
274
170
Guys, any idea how we could check whether it's HDD or a graphic card?
Hello OP,

It sure looks like a graphics card problem. To offer a glimmer of hope, all three of my 2011 imacs had their graphics cards fail. I 'reflowed' mine, and they're all still working nicely. Maybe worth giving it a go?

Cheers,

Razzerman
 

angniempol

macrumors newbie
Original poster
Oct 27, 2017
5
0
Thanks Razzerman! Just one more question as I am a layman here - what does 'reflow' mean in this context? Cheers!
 

Razzerman

macrumors 6502
Sep 11, 2007
274
170
Thanks Razzerman! Just one more question as I am a layman here - what does 'reflow' mean in this context? Cheers!
You can strip down the imac and take part of the graphics card and pop it in the oven for 8-10 minutes and 190°C. This melts the solder and (hopefully) makes the connections good again. Not guaranteed, obviously, but worth a try.

Cheers,

Razzerman
 

angniempol

macrumors newbie
Original poster
Oct 27, 2017
5
0
You can strip down the imac and take part of the graphics card and pop it in the oven for 8-10 minutes and 190°C. This melts the solder and (hopefully) makes the connections good again. Not guaranteed, obviously, but worth a try.

Cheers,

Razzerman
Whaaat? srsly? :D I think I'd rather go for graphic card replacement ;)
 

Sofad

macrumors member
Jan 24, 2006
32
2
Hi angniempol,

search for imac reballing / reflow on ebay.

I did this with my imac 2009, its running fine for a year now.

Video of the process

 
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Razzerman

macrumors 6502
Sep 11, 2007
274
170
Lol, well the wife did give me funny looks when I tried it. All working well so far (touch wood). Kids hammering two of the imac playing War thunder / rocket league / ark survival thing and diablo 3. No problems yet.

Getting apple/someone to do a graphics card replacement may well prove too expensive to be worthwhile. Get a quote first.