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Ersterhernds iMac G5 20 Inch A1076 Project

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Build Log 11 - Intel NUC D54250WYK Installation

No matter which model of iMac G5 is used (I've completed three), they all face one common limitation... there is VERY LIMITED depth to work with. This A1076 model was no exception, in fact it was the shallowest yet of the models I've worked with.

Throughout the build it is absolutely essential to continuously test the fitment of the shell. Its kind of like piecing together a jigsaw puzzle to see where each piece could potentially fit. As each component is added, it must fit within the depth available or else the iMac will not close up properly. The Intel NUC D54250WYK is the thinnest NUC produced to date. It has a clearance slightly less than its i3 predecessors, primarily due to the change to a horizontally mounted mini-HDMI port as opposed to the vertically situated full HDMI port in the i3 versions of the NUC. This was paramount in the fitment of the NUC, I'm really not certain that the i3 would've worked in this build at all due to HDMI height.

Nonetheless, I successfully tested the D54250WYK's HD5000 graphics with this 20" iMac LCD, so the new i5 Haswell version was a go. It had to be fit somewhere inside, yet leave enough room for everything else to fit as well.

I first decided that the original iMac bottom fan housing had to go. All that I needed was the 40mm fan and not all the rest of the bulky plastic which performed essentially no function and took up critical space that I needed for other components. I removed the fan and chucked the rest. As it worked out, the fan housing location would be re-purposed as part of the new Intel NUC location in the iMac.

The Intel NUC has a top mounted cooling unit which is comprised of a heatsink and fan. This solution is compact and effective in keeping the NUC operating temps in check. The cooling unit protrudes upward from the NUC motherboard by about 1/2 of an inch.


NUC cooling fan and heatsink

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I tested the NUC placement inside the iMac in several different locations, all of which were problematic when test-fitting the iMac rear cover over top to close the computer. The midplane of the iMac, a piece of metal that fits between the computer and the LCD, stole precious millimeters of space that were needed to fit the NUC inside.

Here was my solution. I decided to cut away a piece of the iMac midplane in the exact size and shape of the NUC cooling fan, and seat the NUC in the cut-out. This was potentially a bitter-sweet solution because on the plus side it bought me back the much needed millimeters of depth by removing the midplane, but in doing so placed the NUC heatsink directly up against the LCD backlights, a considerable source of heat. Would the NUC operate cool enough with its heatsink seated against the LCD backlight? I wasn't sure, but took a chance and started cutting.


View of the iMac midplane metal cut-out to seat the NUC heatsink and fan deeper than before.
It was very tough metal to cut with the dremel.

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The test fitment of the D54250WYK in its new home worked out great. The cutout allowed the NUC to seat deep enough into the interior to allow the iMac rear cover to fit back on securely.



Successful test-fitment of the NUC D54250WYK
The NUC heatsink and fan are seated recessed into the midplane, up against the LCD behind it.

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The next challenge was the question of how to secure the NUC. Two-sided sticky tape was an option, but not a great one. I wanted a solution that was secure yet would leave the NUC easily removable without having to apply any stress or prying force to the delicate unit. Additionally, the NUC had to be protected from potential shorting against the metal iMac midplane when the rear case cover was reinstalled.

I chose to use the actual threaded standoffs from the NUC case itself. I removed three of them from NUC case and carefully positioned them (attached to the NUC with the stock screws) onto the metal iMac midplane with JB Kwik Weld. It took a few minutes for the Weld to set, and I had a permant solution I was looking for.



JB Welded Intel NUC standoffs
(Note the black electrical taped areas of the iMac midplane to protect the NUC from shorts)

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The final NUC fitment is so tight that one of the protruding furls of the rear case cover actually presses within one millimeter of the mSATA SSD in the NUC. I installed the protective heat pad (included with the NUC) and it can be clearly seen where the rear case cover has left an impression in the soft thermal pad.

Its VERY TIGHT in there. Great care needs to be taken to avoid electrical shorts.


The offending furl on the iMac rear cover

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The impression left on the mSATA SSD from contact with the furl

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The final result is a NUC securely installed with three of its original screws. It doesn't move at all and can be easily removed from the iMac if necessary. Also, the prior concerns I had about heat transfer from the iMac LCD backlights to the NUC heatsink have proved to be a non-issue. The system operates very cool.


IMG_0717.JPG




Ersterhernd
 
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Build Log 12 - Audio Installation

One of the most desirable features of an iMac with it's all-in-one design is that there are no external speakers to clutter up the desktop. The sound quality and design of the internally mounted iMac speakers is remarkably good for desktop use. Re-use of them is imperative for a successful iMac build.

Although the D54250WYK contains an internal sound chip, I chose to go with a proven USB solution that I've used before. It is the Startech ICUSBAUDIOB device. It's plug n play with OSX and provides decent quality microphone and sound function at a reasonable cost.


The Startech ICUSBAUDIOB installed tightly between the NUC motherboard and iMac inverter
Audio and Mic cables come out to the left. USB connectivity comes out to the right in the photo.

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If connected directly to the iMac speakers, USB doesnt provide ample power for volume levels above quiet. Thus, an internal amplifier is also required for proper audio output. This build uses a simple but effective PAM8403 5V amp to perform the task of amplifying the audio signal. Soldering the required wires to it is easy to do, as it ships without pinned connections. I've tried several different types of these amps, but have had the best success with the one pictured below.


5V PAM8403 Amplifier wired and ready to use

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Amplifier, Microphone, Speakers and USB Audio Device all connected

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The results were perfect. The amp gets its 5V supply from a spare 5V USB red wire and it grounds via a 56 Ohm resistor to the iMac PSU. There is no background static or distortion at any volume. The mic works well where situated at the bottom of the iMac. Google Chrome voice searches work every time.


Ersterhernd
 
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Build Log 13 - HDMI to Mini HDMI Conversion

Although other types of connection cabling could be used, I chose to use a short 5 inch converter cable to plug into the Haswell NUC's Mini HDMI port. The product link is here.


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I filed off the irregular edges of the housing so it was flat, then used strong 3M sticky pads to firmly secure the adapter cable to the midplane. There is little if any stress on the fragile NUC miniHDMI port so the cable will not come loose over time.


IMG_0712.JPG




Ersterhernd
 
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Build Log 14 - Apple A1181 Bluetooth Installation

Using Apple's own bluetooth module gives clean and predictable function, including after a re-wake from sleep mode. The module can be had cheap on eBay, and is easy to install.


Here's the wiring guide for installation to a USB port
(Make sure the red wire does NOT get connected to a USB port 5V)

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The location of the BT antenna is on the bottom of the iMac as shown below

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The signal strength is very good in that location. Note the RSSI value of -55

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The Apple Trackpad even works when navigating inside the NUC BIOS without OSX loaded.



Ersterhernd
 
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Build Log 15 - WiFi Installation

This build uses a BCM94322HM8L Broadcom WiFi mini PCI-E card. The antennas used are genuine Apple parts from a 24" White iMac. They work great, giving me full speed (around 10MB/sec) across my local network. They are mounted up in the very top of the iMac, as the lengths were plenty long to reach from the NUC (18" and 24"). Best part is, I didn't even know I had them until searching through my hardware supply box a couple of weeks ago. :thumbup:


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Ersterhernd
 
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Build Log 16 - SSD Storage

There are two physical drives in this iMac. Intel included a SATA port on the NUC D54250WYK in addition to the mSATA storage of previous NUC versions. A Crucial M4 128GB and Intel 530 Series 120GB form the storage installed in the NUC.

It took careful planning to ensure that both drives actually fit in this computer. The Crucial mSATA drive on the NUC came precariously close to the rear iMac cover, so close in fact that it had to be protected from shorting out against the exterior metal. See this link for details on that.

The Intel 530 mounting was a challenge because the only place it could be situated was directly in line with the rear hinge assembly of the iMac. Fortunately, the SSD is thin enough that the hinge doesn't contact it, but it was very close.


Photos showing the hinge protrusion into the SSD location

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The end result is an iMac with two physical drives, thanks to Intel's Haswell NUC.


Ersterhernd
 
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Yet another awesome build from you. My plans to mod my G4 over the summer fell through, as I simply do not have the expertise and patience necessary to complete this. Although you did not post the OS X Installation process yet, did you use Clover, Chimera or Chameleon? Also, why not go with Bluetooth and WiFi modules that support Handoff and continuity?
 
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Build Log 09 - Apple Startup Chime

The startup chime (or 'bong' as some people call it) is a nice touch for a G5 build. I haven't yet figured a way to play it over the system internal speakers as the original iMac did and don't know if its even possible, but a basic mono playback setup works good too.

The setup is simple, it uses a Picaxe microcontroller that simply sends a single high output to the Playe pin of an Arduino ISD1820 sound recorder. This ISD1820 has a recorded chime sound in its memory which plays once and only once at startup. The speaker used is from an iMac G4.



Arduino ISD1820 and Apple G4 Speaker

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iMac A1076 Startup Video with Chime

[video=youtube;CyXzjWAAi-Q]https://www.youtube.com/watch?v=CyXzjWAAi-Q&list=UUKec_H3wAJbsvZsYh6aGObw[/video]



For complete details of see this link.



Ersterhernd

Hello,

How did you manage the black boot screen with the apple logo with progress bar? With LegacyLogo set to No, I see the tonymac logo without progressbar...
Could you explain this? Your bootscreen looks beautyful :)
 
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