IMAC shutting down

[Tahnee Anne]

Hi Brian ,

I currently have a 27in iMac late 2012 with 8gb ram. I bought it second hand about a year and half ago and it has been randomly shutting down in the last few months. A local tech seems to believe it needs a new GPU and has quoted me around ($500AU), however I'm hesitant to fork out that money if it doesn't fix the problem. 

Would you recommend trying the fix or a new computer? If a new computer, what should I be looking at? I currently use it for editing large RAW files in photoshop. 

Any advice would be greatly appreciated.

Thanks

Tahnee

[Brian]

A local tech? Is this an Authorized Apple Repair Center and a Authorized Tech? 

The reason that I’m asking this is that Apple does not sell parts to 3rd (unauthorized) parties and that the newer iMacs are sealed with a special glue which you can’t buy locally. If your iMac does not have a DVD Drive in it, it’s one of these newer iMacs with the special glue. 

As far as replacing the GPU, I do not agree with that. My first guess is a bad capacitor on the power supply board is the culprit. I suspect that when doing things like editing video or even editing large photos, that the motherboard is requesting more power and the P/S can't handle that load. So it shuts down. I would replace the power supply first. 

Yes, it’s true that Apple had a semi-recall on the 2011 & 2012 27” iMacs that suffered from distorted video and other weird flickering problems that were the result of a bad GPU, (aka video board,) but that problem never shutdown the computer. This shutdown problem is a common one and it's not just you.

So my two cents worth: Get the Power Supply replaced at an Authorized Apple Repair Center. It’s a “normal” problem and is way cheaper to fix rather than spending $2000 or more for a new iMac.

EDIT: It seems that ifixit now supplies the glue strips that secure the display panel to the unit and also has a 3rd party replacement power supply. It's a PITA type of repair, as is most All-in-One computers, and there are special tools to help you during the repair process. If you were to do it yourself, or someone was going to do it for you, make sure you have those extra tools, they make things a lot easier, especially when you put things back together.

Here is a video demonstrating the special tools and the disassemble procedure for a 2012 iMac. Even though they cover the removal of the main fan, the power supply is pretty simple to remove. The tough part is getting the friggin' display panel off. It's both heavy, fragile AND expensive.   

 

[Tahnee Anne]

Thank you so much for your reply Brian. 
My initial thought was power supply as I had googled the problem I was having and that seemed to be the most common cause. However, the computer tech I spoke to disagreed. 

I have started turning my computer off at the wall after I shut it down. So far it hasn't been doing any random shut downs. 
If I continue to have problems with it, I will take it to an apple centre instead. 
Thanks again for your time, much appreciated. 

[Brian]

Right. One of the "fixes" that people have done, is to unplug the power cord from the computer for a period of time or flip a switch that turns off the power at the power outlet. Some choose 15-30 seconds, others choose an hour or so. This usually sets the PRAM on the motherboard, and will seem to "fix" the problem in the short term, however the problem will come back eventually.

How about this idea...replace the power supply AND video card at the same time. While you might pay a little more in parts, you will save in terms of labor since it's already open.

I still say it's the power supply.

[Tahnee Anne]

Thanks Brian, Currently on hold with Apple to get a quote on both items