How I Turned a 2015 iMac 5K Into a Monitor

If you have got an old 27-inch iMac 5K collecting dust, the most valuable part of it is almost certainly the display. The 5120 x 2880 Retina panel is comparable to monitors that cost well over a thousand pounds, and yet the machine itself might be worth next to nothing as a computer. That was exactly where I found myself with a 2015 iMac 5K that was no longer fit for daily use.

Rather than send it off to be recycled, I stripped it down and repurposed the one component that still had real value: the screen. With a display converter board, a power supply and a bit of patience, I turned my iMac 5K into an external monitor for a fraction of what a new 5K display would have cost.

I am planning to do this project again and film the whole process for my YouTube channel. If you want to see that, subscribe so you do not miss it.

What You Need to Convert an iMac 5K Display

The key component is a display converter board. The one I used connects directly to the iMac's internal display connectors and provides DisplayPort 1.4 and HDMI 2.0 output. Over DisplayPort, you get the full 5120 x 2880 resolution at 60Hz. Over HDMI, it maxes out at 3840 x 2160 at 60Hz, which is still a sharp picture but not the native 5K.

The board cost me £177.68, plus VAT on import into the UK. I sourced mine from eBay. You will also need a 12V 6A power supply to run the board, which I picked up from Amazon for a few pounds.

Disassembling the iMac

With the parts ordered, the next step was taking the iMac apart. This means removing the display, stripping out the logic board, storage, fans and every other internal component. A word of caution: be very careful not to touch the exposed traces on the power supply unit. Even when unplugged, capacitors on the PSU can hold a charge.

I would strongly recommend following iFixit's teardown guide for whichever iMac model you have. It walks through each step clearly and will save you from accidentally damaging the display cable or the panel itself. You can spot my iFixit toolkit in the photo below.

Once you have removed every component, you should be left with a bare aluminium chassis. The screw mounts, the VESA plate area and the hinge mechanism are all that remain. It looks surprisingly empty inside.

Installing the Converter Board

With the chassis empty, I mounted the converter board and connected it to the display panel. The board sits on the back of the panel itself and connects via the iMac's original display cable. The small green control board with its physical buttons connects via a ribbon cable and sits off to the side. This is what handles input switching, brightness and the OSD menu.

Testing Before Reassembly

Before putting everything back together, I connected the converter board to the screen outside the chassis. This is a step I would strongly recommend. If something is wrong with the board or the connections, you want to find out before you have sealed the screen back into the housing.

I plugged in a DisplayPort cable from my MacBook, powered on the board and the 5K panel lit up perfectly. You can see in the macOS Display settings that it is recognised at its full native resolution, running at 60Hz. Seeing that Retina display working as a standalone external monitor for the first time was genuinely satisfying.

Putting It All Back Together

The final step was fitting everything back into the iMac shell. I ran both the power cable and the DisplayPort cable out through the old RAM hatch door on the back of the iMac. It is not the most elegant cable routing, but it works and keeps the front looking clean.

For reattaching the screen to the chassis, you can buy adhesive strips made specifically for iMac screen removal and reattachment. I will be honest though: at the time of the original build, mine was held on with tape. As they say, there is nothing more permanent than a temporary solution.

I did consider mounting the 12V power brick inside the iMac chassis and wiring it to the original kettle plug connector on the back. It would have made for a much tidier single-cable setup. Ultimately I decided against it, because if the power supply ever failed, I would need to peel the screen off again to replace it. Having the brick external means I can swap it out in seconds.

Was It Worth Converting an Old iMac Into a Monitor?

Without question. The benefits were twofold. First, it gave a second life to a machine that was otherwise headed for e-waste. The computer inside was outdated, but the display is still stunning. Second, it saved me a significant amount of money. A new 5K monitor with comparable specifications would have cost several times more than the roughly £200 I spent on the converter board and power supply.

Beyond the cost saving, having a high-resolution external display has noticeably improved my day-to-day workflow. More screen real estate at this pixel density makes a real difference whether you are coding, editing photos or just managing multiple windows.

If you have a 2015 (or similar era) 27-inch iMac gathering dust, this is one of the best ways to get value out of it. The whole process took me an afternoon, and the result is a 5K display that I use every single day.

As I mentioned, I am planning to redo this build on camera for a proper step-by-step video. Subscribe on YouTube if you want to see that when it goes live.

FAQ

Can you use any iMac as an external monitor?

Not with this method. This converter board approach works specifically with 27-inch 5K iMac models (2014 and 2015 in particular). The display connector varies between models, so you need to match the converter board to your specific iMac. Apple's own Target Display Mode was removed after 2014, and software alternatives like Luna Display work but introduce latency and do not always support full 5K resolution.

How much does it cost to convert an iMac 5K into a monitor?

The display converter board cost me £177.68 plus UK import VAT, and the 12V 6A power supply was a few pounds from Amazon. All in, the project came to around £200, which is a fraction of what a comparable new 5K display costs.

Is the image quality as good as a dedicated 5K monitor?

Over DisplayPort, the converted iMac runs at its full native 5120 x 2880 resolution at 60Hz. The panel itself is the same Retina display Apple originally fitted, so the image quality is identical to what the iMac produced when it was a working computer.