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I wonder can't you just use LM270QQ1 LCD from iMac 27" with controller board from LG Ultrafine 5K monitor since LCD are almost identical? I guess you just need to figure out how to connect backlight.
 
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Just wanted to chime in to share my completed iMac 5K Franken-Monitor, which I’ve finally gotten around to finishing thanks in large part to the many brilliant contributors in this thread.

It’s a fairly modest build powered by a StoneTaskin FA1 (which I have to say I’m very pleased with) but I did make some alterations of my own, including some custom 3D printed parts such as the board mount, fan exhaust shroud, power supply mount, joystick adapter, cable lock, and port inserts. If there’s enough interest perhaps I’ll getting around to sharing those files once I’ve had time to clean them up a bit.

The speaker crossovers are just simple 2-way single-order units including a 4.7µF capacitor and a 0.15mH inductor wired in parallel. I did find for whatever reason that reversing the polarity of the woofer did improve the sound quality somewhat, contrary to other reports in this thread. In fact I was pleasantly surprised by the quality of the audio when driven by the fairly weak integrated amp in the FA1, I was fully expecting to have to use a separate amplifier but was delighted to discover that the integrated unit was plenty powerful to drive the speakers to an adequate volume for my use case without noticeable distortion. I did however have to EQ them quite substantially to correct for some of the resonant peaks and inconsistencies others have mentioned in this thread, but after doing so I think they sound pretty good.

I was also able to find a switched 5V output on the FA1 in the form of the green status led on the OSD control board, I was then able to use this as a control signal for a little switching MOSFET I found on Amazon, which in turn allows the fan to be switched on and off in sync with the display controller (including in standby mode).

Anyways, just wanted to thank everyone who’s contributed so much to this thread, especially: @Xarl-li, @PaulD-UK, @5lives. I have some other details about the project I’d like to share at some point, but rather than clutter this thread further I might just make a blog post or something and link to it here.

Cheers!
 

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Trying to make some transfer board.
Do U have some good ideas?
 

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Hi!
I am in the middle of my conversion of a late 2015 retina 4K iMAC 21.5" to monitor.
Have bought and just tried the CY.R9513 v5 board for imac A1418.
Connected with a HDMI 2.1 cable from my macbook i am getting a weired and sqewed display.
Seller ask me to try a different cable or update firmware. Dont have another cable home at the moment. I think i have seen someone else having this trouble somewhere but cannot reccon, and cannot find again.
(sorry for bad focused picture with reflection from window. The picture on screen is sharp, but skewed. The menu for screen settings is straight.)
Any ideas?
 

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@Mowgli10L
Because the OSD is normal and straight the R9513 is connecting to the screen normally.
So that means the skew problem is between the MacBook and the R9513.

All these conversion boards work best when connected through the DisplayPort input, so the best thing is to get a USB-C to DisplayPort 4K cable, and try that.
For 5K iMac conversions it needs to be an 8K DP 1.4 cable, but for 4K/60 just a 4K cable should be OK.

I don't know enough about these boards to be sure it's a cable problem, because it might be that the firmware on the board is not right for your screen.
Normal 4K is 3840x2160, but A1418 4K iMacs have a screen that is 4096x2304, so they presumably have different firmware to enable that.

Did you tell your seller that you needed the R9513 to work with an iMac, so they could flash the board with the correct firmware??
 
@Mowgli10L
Because the OSD is normal and straight the R9513 is connecting to the screen normally.
So that means the skew problem is between the MacBook and the R9513.

All these conversion boards work best when connected through the DisplayPort input, so the best thing is to get a USB-C to DisplayPort 4K cable, and try that.
For 5K iMac conversions it needs to be an 8K DP 1.4 cable, but for 4K/60 just a 4K cable should be OK.

I don't know enough about these boards to be sure it's a cable problem, because it might be that the firmware on the board is not right for your screen.
Normal 4K is 3840x2160, but A1418 4K iMacs have a screen that is 4096x2304, so they presumably have different firmware to enable that.

Did you tell your seller that you needed the R9513 to work with an iMac, so they could flash the board with the correct firmware??
 
Hi Paul and thanx for reply!
yeah, the seller was informed that it was for an iMac conversion. He also got the modelnumber written on the screen and picture of connectors. A strange thing was that he believed my picture of display connection and model number was from different screens...! Argued that they were incompatible. The modelnumber is for a non 4K display (LM215WF3SDD5), but the connection was is a 4K display, so have gotten a board for the (LM215UH1-SDA1)... he believed it was the wrong sticker attached in the end...so ofcourse here might be an issue as well. But also on the iFixit site (https://www.ifixit.com/Answers/View/627222/Screen+Replacement+for+iMac+4K) it says that the screen is supposed to be the LM215UH1-SDA1. And since im the only owner of the computer, i am absolutely positive it is a late 2015 4K retina iMac 21.5". So i figuered the bad sticker was a plausible explanation.

Will get a thunderbolt-DP 4K cable tomorrow and try that.
 
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@valexv You're completely right, clearance is extremely tight; don't know what I was thinking when I designed it.

I've uploaded a low profile version of the board that I think will provide better access to the ports (see pic below):

iMac 5K conversion using SA1 board

This project has been entertaining (forced me learn about 3d modeling) but I think I'm ready to close it out - most likely will not try to reuse the speakers (at least for now) since the SA1 board amplifier is supposed to not be very good. Will upload the remaining models once I'm done.

View attachment 2495041
Thanks again! I had your first version printed, I think I can get it to fit with some fiddling :)
What screws are you using to fix the SA1 to the 3D-printed board?
 
@Mowgli10L
Because the OSD is normal and straight the R9513 is connecting to the screen normally.
So that means the skew problem is between the MacBook and the R9513.

All these conversion boards work best when connected through the DisplayPort input, so the best thing is to get a USB-C to DisplayPort 4K cable, and try that.
For 5K iMac conversions it needs to be an 8K DP 1.4 cable, but for 4K/60 just a 4K cable should be OK.

I don't know enough about these boards to be sure it's a cable problem, because it might be that the firmware on the board is not right for your screen.
Normal 4K is 3840x2160, but A1418 4K iMacs have a screen that is 4096x2304, so they presumably have different firmware to enable that.

Did you tell your seller that you needed the R9513 to work with an iMac, so they could flash the board with the correct firmware??
Hi again! Yes, with a USB-c to DP it works just fine! Very strange behavior on the HDMI cable though.. Wonder if it was a bad HDMI-cable or if the HDMI input to the board itself is bad?
In my build I try to make "nice" connections ala @Aiwi by enlarging some original connection holes in the case for the new connections (DP & HDMI), but considering to drop the HDMI if it doesent work...
 
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If the board works perfectly with DP, the likelihood is that the iMac-specific 4096x2304 firmware hasn't been properly implemented for HDMI, just for DP.
I guess the skew comes from the HDMI 3840x2160 /4096x2304 mismatch....

Macs work with DP internally and through the USB-C ports, and I think the HDMI port output is derived by converting DP to HDMI internally.
 
If the board works perfectly with DP, the likelihood is that the iMac-specific 4096x2304 firmware hasn't been properly implemented for HDMI, just for DP.
I guess the skew comes from the HDMI 3840x2160 /4096x2304 mismatch....

Macs work with DP internally and through the USB-C ports, and I think the HDMI port output is derived by converting DP to HDMI internally.
Ah, OK. And i guess its not so simple to just update to correct firmware on my own. So i guess i stick to DP.
 
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If the board works perfectly with DP, the likelihood is that the iMac-specific 4096x2304 firmware hasn't been properly implemented for HDMI, just for DP.
I guess the skew comes from the HDMI 3840x2160 /4096x2304 mismatch....

Macs work with DP internally and through the USB-C ports, and I think the HDMI port output is derived by converting DP to HDMI internally.
Well. End of story. Now the thing is dead....Displays no input and goes to sleep. I guess i f*kd up trying to cram everything into the case, moving things around to much and finally breaking something. Big bummer. Just got to buy a new board.....
 
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