Getting creative with a destroyed 2017 iMac?


#1

I have a reasonably interesting situation here. I’ve come across a destroyed 2017 iMac 27", with a completely obliterated screen, enclosure and power supply. The screen is shattered into thousands of pieces, the housing is bent and several welds are broken, and the power supply has ignited and burned up where the LCD was pushed back into it. The Hard Drive was totalled as well, but that was removed along with the Flash module during recycling.

It’s anyone’s guess what could have happened to it, but I suspect it fell from somewhere, or off something.

The Logic Board however should be a runner, and a decent one at that. It’s configured with a 3.8GHz i5 Quad “Kaby Lake” CPU, paired with an AMD Radeon Pro 580 8GB Graphics Processor.

I considered parting out the board and removing the socketed Kaby Lake CPU, as that’s worth about $300 itself, but I can’t help but wonder if the board itself could be reverse engineered so I can take advantage of that AMD GPU.

I tossed around the idea of running the board in another enclosure, but hit some roadblocks there. While the board only requires 12V and GND to power it, there are two temperature sensors (PSU and LCD) that cause the board to throttle back if they’re not detected by the SMC. So some reverse engineering of the board to re-add these missing sensors is required. (Because schematics aren’t exactly readily available for these boards.) There’s also the issue of fabricating a sheet metal enclosure to hold the board, PSU, drives, connectors and wireless antennas.

That said, for such an expensive part, there isn’t a massive market for selling Logic Boards either. The machines are still under warranty, and so demand for replacement boards is low, something that won’t change for at least another three years. As it stands, the bare CPU alone is probably worth more than the entire board - it’s just a shame, considering it also houses such a powerful graphics chip.

Anyone have any ideas? Or should I just part out or scrap the board as well?


#2

You can’t salvage the sensors from the otherwise broken bits? Or are they all integrated into the screen/PSU?

It might be worth looking at an iFixIt teardown to see if you can’t work out what the temp sensors are. Even emailing them if you can’t see the sensor might be worth a shot.

Sounds like a fun project though :smiley:


#3

Not sheet metal.

Wood.

Old School.

Worked for the Apple 1. :slight_smile:

Outside of that quip, I’ve no real suggestions. I expect even throttled it would work pretty fast? Capable of performing some useful processing - HTPC or something?


#4

In the past I’ve ordered replacement SMC compatible sensors for a Mac mini when a brittle cable snapped as I removed it. At that time most of the Apple temp sensors used the same connector on the logic board - is that still the case with the 2017? In the tech manuals it tells you where the temp sensors connect to the logic board yeh?


#5

The sensors are integrated into the components now, so the PSU sensor is on the Power Supply PCB, the LCD sensor is on the LCD controller PCB, and so on. No dedicated connectors, the sensor data is fed down the interconnect cables between those parts, like the eDP cable.

Addressing the issue will involve finding the SMC lines on the board and attaching input and output wires to each, then connecting a sensor to those. It’s easy if one can source the schematic and board view files, but being Apple proprietary property, it involves negotiating with someone out of Russia to find them, if they’re even available at all. I don’t believe they are for the 5K machines.

Otherwise, some probing around at the connectors themselves may reveal which lines need to be tapped. The Power Supply one isn’t difficult, but the LCD one is. I’ve kept the broken LCD board and PSU for further study though.

Apparently the performance reduction is around 75% of the processing capabilities of the machine, so a pretty significant decrease.

Good call on the wood though, done properly it could look quite impressive, but I’d need to improve on the fifth-grade creative arts level of woodworking knowledge first.


#6

Shoehorn it into one of those vintage PC boxes you’ve been restoring!

Wood is fun but then you’ll need to line it for shielding


#7

The shape of the board would actually fit pretty well in something similar to a Commodore Amiga or 64C case, or anything with a wedge profile at that. If I can make the board run without the PSU and LCD sensors present (even if I have to make debug sensors it’s fine, I just need to find out where to solder the wires to) then this would be a logical next step since a wedge case is relatively easy to make.


#8

Just posting an update to this, but I passed the board on to a co-worker to mess around with. We have a couple of options so far:

  • Hammer the iMac enclosure as straight as possible, weld or tack the broken standoffs back on, and install the board with a replacement power supply. LCD removed and disabled, perhaps with a perspex cover over the live electronics.

  • Make a carrier to support the board and power supply, and mount it entirely within a Mac Pro enclosure or whatever we have on hand.

I wanted to continue with the build myself, but I don’t run games or other applications with processing requirements intensive enough to justify it, and between the other projects I have on hand and wanting to get out more and see people instead of sitting around reading schematics and soldering, it was probably too much to take on at this time. That said I’ll continue to help with it and if we do anything interesting, I’ll post the results.