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IC's 20" iMac NUC Flowerpot

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IMG_7623.jpg
Picked this guy up yesterday for $80 with some additional accessories. It's a 1.25GHz 20" iMac G4 USB 2.0, circa 2003. After reading about all the mods forum members have done, I have decided to go with a NUC, and per Ersterhernd's recommendations and testing, I have selected an Ivy Bridge i3 NUC, most likely the DC3217BY model, and have elected to NOT reuse the original PSU.

The key issues here are going to be:

Powering the LCD and avoiding static
- Ersterhernd had many issues with what we believe to be EMI.​
Reuse the original power cord
- to maintain the outward appearance of the original G4.​
Maintain NUC upgradability
- in another 11 years or so, this guy might need another upgrade.​
Full Display Brightness
- I don't think I am going to make the display dim via a microcontroller, so I would rather it be at full brightness, which means a PicoPSU with enough wattage to support it.​
Budget Features
- It's not huge that this thing has a ton of features at the moment. Those can be added later when I have the funds. Basic wiring and full NUC functionality are the main goals for the initial aspect of this project.

Obviously the display conversion is going to be the biggest part. Powering the backlight and wiring the conversion to DVI and then to HDMI is going to be most of the work, then it will just be port management and cable management to adapt the NUC ports and extend them to the iMac body. Use of the internal speakers would be a big plus, especially if I can get the Microphone rewired to work with the NUC.

So first, does anyone have a recommendation on a PicoPSU? The one Ersterhernd used looks to run around $50 USD, I'm hoping I can find one that works just as well for closer to $30. I've already gone ahead and purchased the upconverter at Ersterhernd's recommendation, since the shipping times are less than optimal. So it looks like I'm looking to get a 12V PicoPSU with enough power to supply power to the 20" backlight at full brightness.

Hope this project goes well. Thanks for all your help in advance, and a special thanks to Ersterhernd and everyone else who inspired the undertaking of this project.

-IC
 
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So first, does anyone have a recommendation on a PicoPSU? The one Ersterhernd used looks to run around $50 USD, I'm hoping I can find one that works just as well for closer to $30. I've already gone ahead and purchased the upconverter at Ersterhernd's recommendation, since the shipping times are less than optimal. So it looks like I'm looking to get a 12V PicoPSU with enough power to supply power to the 20" backlight at full brightness.


Hi IC, I'm not sure what your power map is going to be, but the PicoPSU will need to be a Wide Input version to handle the 19V supply from your Power Brick. A standard 12V Pico won't work with a simple split from the power brick, as the NUC requires 19V +- 1V or so. Ensure your power brick is robust enough (around 90W) to supply the LCD, Backlights, Fans and NUC. The thin Antec one I used worked great. The brick included with the NUC is only 65W, so you'd be right at threshold even idling.

I believe the PicoPSU comes in two wide input flavors, the WI-25-120 is the cheaper of the two. Perhaps you have different plans, I'm not sure.

Looks like it'll be a great project.


Cheers!
 
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Strip iMac & 92mm Fan

With the weekend approaching and a morning off of work, I've made my first disassembly of the iMac. Using the iFixit Guide for the 17 inch version of this model, teardown was easy. I've saved the hard drive and stuck it in my G4 tower, since this guy came with a good amount of software. The old 92mm Exhaust Fan has been replaced with a Noctua NF-B9 92mm fan for optimal airflow and silence. If resources permit, I may add a fan controller as well with the built in Pulse-Width Modulation capability. This Saturday will be the first real work day, I hope to accomplish the TMDS to DVI conversion with a friend of mine and splice the power supply. With parts arriving daily, it's just a matter of time until the display is up and running.

Below you can see the iMac laid out on my bed with the PSU & Drive Cage removed, at the top of the dome you can see the new Noctua fan mounted where the old SuperRed fan was. (Incredible how dirty that thing was.)
IMG_9675.jpg
IMG_4959.jpg

Big events at work these next two days, but Saturday night I have time set aside to do some more work with a friend of mine who is a bit more skilled at wiring than I am. I've pulled the diagrams from the DremelJunkie site (wayback machine is a great resource) for the TMDS modding. Will keep you all posted, and once again thanks for your experimentation and work to make this project easier.
-IC
 
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TMDS to DVI Conversion

Step one was breaking out the DVI conversion. Unfortunately, the 12V-24V step up converter will not be here until Friday, so testing and power connection is going to have to take a back seat. With the help of WayBack Machine and the DremelJunkie documentation, the DVI pinout was very straightforward.
IMG_4154.jpg
Pictured above is the grey and black LCD pin broken out of its original casing. From there, it was easy to separate the cables and appropriate each wire to the correct DVI pin.
IMG_4156.jpg
Above is a picture of the two LCD cables wired into the DVI pins, aside from the wires that receive power and the wires that go to ground. In the black shrink wrap is the 1kohm resistor jumping pins 14 and 16, nicely condensed and zip tied. The rest of the wiring for the display will be done next weekend, provided the step up converter arrives on time.
 
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PSU Placement & Modifications

I've elected to place the Antec 90W Power Brick in the space just to the right of the drive cage, rather than above it.
IMG_4157.jpg

The red rectangle represents where the power brick would ideally fit. Unfortunately, the housing of the power brick was just barely too large, so it was time to make some modifications.
IMG_4158.jpg

The Power Brick was carefully sawed open to remove the black housing. We then removed the two prong power connector from the AC cord and soldered new wire to the actual circuit board of the power brick. The removed housing and the added wire can be seen here:
IMG_4159.jpg

Afterwards, the power brick was wrapped in duct tape and inserted temporarily into the iMac base. In the photo below, it is being held in by a velcro wrap just for fitting purposes, and will eventually be held on by heavy duty velcro. The original iMac AC filter will be retained, and eventually, the original iMac wires will be attached to the new AC wires on the Power Brick. In the brick modding, both the 19V output and the AC input wires were routed to the back of the brick, allowing minimal wiring to be added to the brick for the AC connections.
IMG_4160.jpg

Now, it's just a waiting game for the step up converter. :beachball:

I'd also like to thank my friend Kyle for his help with this project and his continued expertise in electrical work.

Happy modding,
-IC
 
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Wow your progress looks terrific IC! I really like the PSU mod, that worked out great. Btw if you want to test your video without the upconverter, just use the 24V line from the iMac G4 PSU for now. Thats what I did while I waited for my chinese upconverter.

One recommendation from your photos. Perhaps solder in a heavy ground wire from the cable shield to the DVI ground pin. This will help eliminate EMI in your video circuit, and is easy to do while its still all pulled apart. Just use caution that you dont overheat the shielding of the cable.


bxs1g.jpg




Cheers!
 
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Thanks for the recommendation, that is probably a good idea there. Eventually, the whole converter will be wrapped up and properly EMI shielded. Unfortunately, the G4 PSU has been sold to fund the project (for quite a bit, I might add, surprising how much original parts go for). :crazy:
-IC
 
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Hi InsaneCultist

Good to see a new G4 project. Looks good so far. :thumbup:

One recommendation from your photos. Perhaps solder in a heavy ground wire from the cable shield to the DVI ground pin.

Ersterhernd's right. You should do that. I did it too in my HemiMac.

Good luck.

MacTester
 
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Hi InsaneCultist

Good to see an new G4 project. Looks good so far. :thumb up:



Ersterhernd's right. You should do that. I did it too in my HemiMac.

Good luck.

MacTester

Thanks MacTester and Ersterhernd for the advice, that's for sure next on the list to do, then. The Up-Converter arrived today, so this weekend will be another time to work. Hopefully my velcro will arrive shortly and allow me to fasten things into place so I can complete the design and fittings...

Will keep you all posted...

-IC
 
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Reuse of AC Power Filter & Up Converter Mounting

Since the Antec Power Brick mod, there have been two wires that were attached to the Power Brick that will be attached to the original AC filter. Below, you can see a picture of the original AC filter attached to the brown wires spliced to the Power Brick via wire couplers. You can also see the DVI shielding soldered to the ground pin on the DVI connector. Thanks again to Ersterhernd and MacTester for the recommendation.

IMG_4176.jpg

With everything rigged up, it was time to test the Antec Power Brick. With the wires all connected, the voltmeter gives a nice 19V reading from the Power Brick.

IMG_4175.jpg

The Up Converter has been mounted in the drive cage in the picture below. It is attached with industrial strength Velcro, which is also now securing the Power Brick (not pictured.) You can also see the PicoPSU mounted to the left (also with Velcro.)

IMG_4179.jpg

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

On another note, I've gone and messed up the TMDS wiring. :banghead:
I've screwed up the VEDID wiring and attached the 3.3V Red Wire to the wrong section. The backlight comes on all fine once the DVI cable is plugged in, but stays on once the DVI cable is removed, plus there's no picture. Time to remove some heat shrink and fix some tiny wires.... :beachball:

Will update soon...
-IC
 
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