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iMac G4 20" Mod

Joined
Oct 30, 2017
Messages
4
Motherboard
Lenovo ThinkPad X250
CPU
Intel Core i3 5010U
Graphics
Intel HD5500
Intro
About a year ago I found this subforum and I immediately wanted to do a mod myself. So I started looking on our local "Craigslist" but there where only 15" and 17" G4s at that time, there where 20" G5 on sale but they are quite overpriced for the obsolete machines that they are. I waited a bit and G4 20" showed for sale.
The machine is in quite good shape, a bit dirty on the edges but overall pretty white. It starts and runs, the only thing bad was the little lithium battery on the system board. I also bought a G4 15" with Pro Speakers but in quite bad shape, the LCD was shattered and the system board was dead but I only paid 10€. Because the 20" is quite rare and I don't want to destroy a working iMac so I will take the LCD off of the 20" and place it on the 15" base. None of the LCD conectors will be cut or modified so I can assemble the 20" back together if I want.
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Here is the 20" still assembled.
 
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Joined
Oct 30, 2017
Messages
4
Motherboard
Lenovo ThinkPad X250
CPU
Intel Core i3 5010U
Graphics
Intel HD5500
IO Panel
Today I started working on the IO panel, first I wanted to the desolder the GPU but I couldn't heat it enough with my hot air rework gun. So I took outside and I cut off the part I needed.
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After that I took a thin HDMI cable and cut one end off and then I soldered it to the board. It took a while to get everything right because there where some internal shorts to ground because of the cutting. I wraped the cable tightly because that reduced the interference dramatically, now it's almost 100% clean. After that I soldered a header cable for 2 of the USB 2.0 ports and for the Ethernet port which works at full gigabit speed now.
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The only thing left is the audio jack and maybe adding a USB 3.0 port.
 
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Joined
Oct 30, 2017
Messages
4
Motherboard
Lenovo ThinkPad X250
CPU
Intel Core i3 5010U
Graphics
Intel HD5500
DIY PSU fail

So I had few buck converters, relays and MOSFETs laying around, so I thought let's build my own pico PSU and use the original PSU for the AC/DC conversion. Oh boy what a waste of time, couldn't get my AsRock H81M-ITX, 4770k and 16GB DDR3 combo to boot, it could a be problem with power sequencing or maybe to big of a voltage drop because the PSU has only 120W. So in goes my J1900 based board that has a built-in DC/DC converter, I also took the time a wired the LCD, inverter and SATA power to one Molex connector so it's easier to swap the temporary motherboard. I also have to buy a i3 because the 4770k is used in my main rig and the i3 will be easier on the iMac PSU. One of the caps on the original PSU bulged so I removed it and now I'm waiting for the replacement part. Also I'm thinking about putting a cheap NVMe SSD just for fun
There will be probably no new posts until my pico PSU arrives from China and a new boost converter because this one keeps burning though Schottky diodes.
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Joined
Oct 30, 2017
Messages
4
Motherboard
Lenovo ThinkPad X250
CPU
Intel Core i3 5010U
Graphics
Intel HD5500
Wiring update

The new step up converter arrived so I took a little time to clean up wiring. First off was the HDMI cable, I was getting some red dot interference so I took a cooper foil strip from the original DVD drive and wrapped it around the HDMI cable and soldered it to the HDMI connector shield. I just a bit of hot glue to give it some strain relief. I also got a A1181 BT module and A1016 keyboard. For now I'm still running Windows 10 because I still haven't got a LGA1150 i3 for my second motherboard. The MP3 module and PAM8403 amp arrived and are working great for the Apple Chime, when I get the replacement 28mm speaker I will put it together. The only problem remaining is the headphone jack detection, there is a older mod here that took advantage of the original headphone jack but I don't know how to implement on my 15" board.

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