20" iMac G4 Intel NUC Ivy Bridge AiO Mod (Videos)

A video demonstration of my updated iMac G4 mod/hack (NUC/Ivy Bridge Mountain Lion Hackintosh)

 

Part 1:

Introduction and General Overview (YouTube Link)

Part 2:

Turning It On and Testing It Out (YouTube Link)

So that pretty much completes this mod.  I have thought about new HD 21.5" LCDs to the top of the arm in a custom LCD case that mimics the iMac G4, but I am not sure that would add very much.  This monitor falls just short of HD and I have not had any issues with it in terms of quality.  Though its something to consider for the future.  I find that larger monitors start to look "awkward" with the base.  Although placing the Cinema Display on the top of the monitor worked.  It wasn't until I went back to the original that I realized it was "off".  It didn't droop or tilt, but it didn't move as smoothly as the original.  The neck was obviously designed very specifically for the native monitor.  This includes not only the weight, but the thickness and shape as weight distribution changes as you tilt and swivel the neck.  Unfortunately, without the R&D budget of apple, its hard to design a new neck, but the old one works beautifully with the native LCD.

I would still like to make this into a touchscreen and perhaps add an iSight.  The awkward size and Mac compatibility issue make this difficult.  While I have a capacitive screen that works, its thick and heavy and would require dramatic hardware changes (LED lighting with custom thin diffuser) or physical changes (altering the LCD case and front bezel).  I am still hopeful that touch films will eventually be readily available, adding touch capability of any size with negligible cha ges in thickness.

Anyway, I'll worry about that later and enjoy this computer for a while.  I have tons of pics from this and previous mods, as well as the ability to fill in gaps with surplus materials.  As such, I'm thinking about putting together a "Moving Picture" Video Guide.  Sort of a compromise between a written and video guide.  I'll be able to explain from start to finish, step by step, how to do this with audio and annotated pics.  Let me know if this sounds at all interesting or useful to anyway.  Thanks for reading/watching.

20" iMac G4 NUC/AiO Ivy Bridge Mod: SUCCESS!

20" iMac G4 / NUC Ivy Bridge Mod

Updates:

I'm happy to report that all problems have been solved and the motherboard fit test was successful.  This is currently the method I would recommend for those that want a 20" Ivy Bridge Hackintosh version of this mod.  As I noted in my previous post, while I initially believed I would not go in the direction of the NUC board, its remarkably small size and simplicity made it by far the best candidate for this mod.

Original vs NUC/DVD - Front

In multiple previous posts I have explained the advantages of having the core elements (processor/motherboard) of the mod at the top of the dome where ventilation is best.  In my previous ECX mod, the board only fit with the optical drive because I did not use the native PSU.  Because I wanted to use the native PSU, I did not believe fitting the optical drive was possible, but with this board it looks like it is going to fit. (Although nothing is definite until this is completed).  This board fits into the slot left vacant by the 3.5" HDD (the mSATA is on the mobo itself).  It pretty much fits into the grooves in the drive chassis requiring no alternation.  For comparison, I have taken side by side photos of the original optical drive and HDD in the drive chassis next to the shorter new dvd optical drive and the NUC occupying that area.  The height is pretty much the same and there is amble room for the connectors to fit as well.

Original vs NUC/DVD - Top

Problem Solving:

With this fitting at the top of the dome, I should have even a little but more room for components than I did with my previous mod.  This is because, there are less port extenders needed and no SSD is required at the bottom of the dome.  It will still be tight, but I have some wiggle room to address the problems that I brought up in my previous post.  Taking them one at a time:

1) USB Ports: A 4 port USB Hub leaves me with only 1 spare USB port, but solves the problem.  The addition of another hub or a larger one is likely.  A USB port supplies the 5V to the PSU.

2) The Fan: The directional fan is connected to the heatsink and I did not want to remove it.  I also wanted to keep the case fan.  Apple's connectors and colors are completely backwards from industry standards (Black is 12V, Red is Ground and the fan out is a 3pin Male connector, not Female).  The fan is also somewhat loud and old, so I decided to replace it.  I bought a Antec 92mm fan that had a molex out (there is no case fan output on the board).  There is a sense pin that I won't be using.  Because I won't have software fan control, I got a model with a 3 speed setting.  I put it on medium to reduce noise and may extend the controller to the back ports or simply leave it on this setting.

Wide Input Pico PSU

While 12V are readily obtainable from the PSU, the problem is that the PSU is always on.  So, the fan will spin as soon as the computer is plugged in, no matter if the computer is on or not.  As the computer does not have any 12V out, I will have to use some kind of switch.  Luckily, the PSU comes natively with a "switch".  The PSU relies on the motherboard to downconvert 12V to 5V then feed 5V back to the PSU to turn on the 24V line that powers the monitor's backlight.  Although there are many other ways to do this, I went with an elegant solution using what I had available.  Keep in mind this is not the only peripheral that needs power.  The optical drive requires 12V and 5V in either a molex or SATA power connector.  Luckily, I had a very small 20 pin PICO power supply with a WIDE INPUT range up to 24V. (Not all PICO PSUs can accept 24V, may sure before you connect).  I spliced the PWR input to the Green wire of the PSU (24V) which connects to the Inverter Wires as well.  I connected the ground to a native PSU ground.  As this is a standard 20 pin ATX based PSU, it won't work without a motherboard unless you ground the On Pin.  I have it connected to a switch, but will likely just leave in a wire, allowing the PSU to turn on as soon as it receives 24V DC input from the native PSU.  This produces the necessary 12V and even a 5V and has both a Molex and SATA power cable out.  I connected the Molex to the Fan (you only need the 12V line and ground), and the SATA to the optical drive.  Now we the peripherals will only turn on when the motherboard itself is turned on.

PICO PSU powering the optical drive

The Bypassed Power Switch

3) Power Switch: I did not want to damage the board, so I simply threaded small wires between the onboard switch and its solder points.  I did this to the front right and back left corners.  This was then wired to the case switch at the bottom of the dome.  These can be easily removed in the future if this board is ever repurposed.  In addition this does not effect the functionality of the original switch in any way.

The case switch I use is from my previous mod. Modeling clay was used to secure a momentary switch directly behind the peg that protrudes from the back of the plastic power button on the back of the iMac dome.

4) Audio: I am sticking with the Turtle Bay USB Audio solution from my last mod.  This allows for a standard 3.5mm audio jack out and also supports a 3.5mm Microphone in.  I have it wired to the microphone in the LCD housing.

5) Bluetooth: I have not found anyone who has had success with any half height mini PCI-E that supports Wifi and Bluetooth with Mac OSX.  So, I am simply going to keep my very small USB bluetooth solution.

6) Optical Drive: I am using a DVD Burner that gets power via the PICO PSU discussed in #2.  The connection to the mobo is via a SATA to USB 2.0 adapter cable.

12V to 19V DC-DC Upconverter

7) Power: While the option of splicing the AC to the to the existing AC plug with the NUC's powerbrick is not a bad one, it is somewhat of a waste of the 180 watt PSU that already exists in the machine.  Not to mention that I'm already including a second PSU (which is really being used only as a downconverter here).  The NUC requires 19V at (at least) 3.7A and the PSU is only supplying 12V (can't use the 24V because its only on with 5V from the motherboard).  Luckily, 19V is the typical notebook operating voltage and therefore upconverters are available.  Though there is a much smaller selection than for more common voltages (24V, 12V, 5V etc).  Many different shapes an sizes are available.  I got one in a familiar shape on ebay from a Chinese manufacturer for $20.  Its relatively small ( I may remove part of the heat sink surrounding it) and is a 12V DC to 19V DC upconverter at 4A.  This is exactly what is required and works flawlessly.

The Upconverter connected to PSU and NUC

The Upconverter gets 12V and Ground in from the Native PSU and sends 19V out.  I had a broken Laptop AC power adapter that had a DC input that perfectly matched the power in plug on the NUC.  The positive is the inside peg and the negative is the outer part.  Using a multimeter I ensured which wire was which and connected this to the power supply via the up converter.

The Fit Test:

The Secured NUC Motherboard

On a side note, I used a rubber sleeve to cover the drive cage where the NUC will go.  After some guess and check, I determined the place where the  NUC and USB connectors seemed to fit the best. To test fit, I used twist ties that went through the screw holes in the grooves intended for the HD and then through the motherboard screw holes.  These will be replaced with plastic locking ties to secure the motherboard in place.
One thing to make sure of is that the wifi antennae which goes through the metal faraday cage (Wifi signal will be severely reduced if the antenna is within the cage) is connected to the wifi card before the board is secured.

Build Pics:

A Mess of Wires, But A Working Mod

Video and Audio Test

Motherboard View

About This Mac Screen

Remaining Issues:

Obviously, there is a lot of cable management to do.  This will get much simpler once connections are directly soldered (connectors removed and alligator wires eliminated).  As I technically have more room at the bottom of the dome than the previous mod (also had a DC converter and a PICO PSU to deal with), I do not believe this will be difficult to fit.  The wire management, however, may be more involved.

There will a paucity of ports.  A 3.5mm audio out, a few USBs, and not much else.  If I had to do it over, I probably would not have bothered spending the extra money on the Thunderbolt equipped version.  There are so few available peripherals and there are so overpriced that I can not even test this. Perhaps this is somewhat future proofing, but I would imagine there will be further upgrades to this board before thunderbolt actually takes off (if it ever does).  That said, I would not have bothered with an ethernet extender anyway.  I've learned with this that the more you do, the more that can go wrong.  I am more than happy to keep it simple.  I also have the option of adding a powered USB hub with the 12V lines in the PSU.  Unlike my previous mod which was very close to its power maximum, this should have room to spare.

Concluding Thoughts:

Untili I have it assembled and have worked with it for a while, I'm cautious about speaking too soon, but I am very optimistic about this project.  Although to Core i5 Sandy Bridge to a Core i3 Ivy Bridge may seem like a lateral move, this board is simply a better fit.  Its lower power, quieter, and everything onboard works.  The incorporation of the native PSU while keeping the optical drive makes this virtually indistinguishable from the original 20" iMac G4.

Hopefully will finish soon! Thanks for reading.

A Great Little Board

A Change of Heart

When I first ordered the Intel NUC, my purpose was to see if this form factor had promise for the future.  I also figured that this small board would be useful to test projects and perhaps even wind up as a little media center somewhere.  In truth, I did not expect to seriously consider this board for the iMac G4 project. After working with this board for a while, I have to admit, its pretty fantastic.  For one, the size is remarkable, especially when it is removed from the case. This makes even ECX boards look big.  Secondly, its dead simple, it uses EFI bios, requires only RAM, a half height WiFi mSATA, and a full size mSATA SSD.  The mSATA in particular makes the system even smaller.  There is no need for even a 2.5" drive and nearly all wires are eliminated in this fashion.

 

As opposed to the other boards, this board only contains a Core i3 processor and there is a paucity of USB ports (only 3), mSATAs (one half height, one full height), an HDMI connector, and either a Ethernet + extra HDMI or Thunderbolt. (Depending on which of the 2 models you choose).



A Look Inside

 Despite these negatives there are other advantages this board has.  The availability of 2 RAM slots for a max of 16GB.  Thunderbolt while (at this point) is expensive and has few compatible devices does leave open impressive possibilities including hubs, a second display, and even a pci express graphics card.  The size also leaves most of the base available as it fits between the native PSU right under the fan and allows you to keep the optical drive (though a USB connection would be needed as there are no regular SATA hookups).

The Software/A Mountain Lion Hackintosh

The only method I use is tonymac's retail Mountain Lion Unibeast/Multibeast install method.  While the other boards took a very long time to get right, this could not have been easier.  I did know in advance to change the graphics to 128MB and of course AHCI instead of IDE (for the SATA controller).  Except for these small changes, there is almost no way to go wrong.  I used the Easy Beast Install with the Mac Mini 6,1 definition.  Now the reason for this is that there isn't much to the board, while other motherboards are loaded with other chipsets for gigabit Ethernet, SATA controllers, Touchscreen controllers, other I/O controllers, and business related QM chipset features, this board is really only about the basics.  But, with hackintoshes, less is more.  Having to clear your CMOS after you mistakenly enable some feature is no fun.  Neither is having to reinstall the OS because you decide to try to get native audio to work one last try.  This makes it very time consuming when it comes time to upgrade your OS.

 

One note,  I have read HDMI audio does require a work around, but this obviously does not apply to this mod.  Without any other audio cable out, a USB audio card will be needed.  But, so far airplay seems to work flawlessly, and can make for a wireless alternative.  So, in short, if a modestly powerful Ivy Bridge Hackintosh is your goal for this mod, I would recommend these boards above the others.  Being the easiest to find and the most affordable also doesn't hurt.

 

About This Mac

 Some Technical Issues to Solve:

1) Ports: 3 USBs is simply not enough and for basic function more is needed.  Thunderbolt hubs are absurdly overpriced right now, but either a Thunderbolt to SATA and/or USB or a regular USB Hub will be needed.  One USB is needed for the 5V "backlight power on" signal.

2) Fan:  there is a directional fan, but due to the faraday cage, I would still like to add the case fan in some manner.  This may involve replacing the existing fan and situating it directly underneath the iMac's case fan, splicing the fan wire to power it.  Or, running both, using the PSU to drive the fan (though a manual control knob may then make sense).

3) Power switch: This is hard soldered to the board.  A bypass will need to be wired up and I am fairly sure this can be done in an easy to reverse way.

4) Audio: A USB audio solution is needed.  This is not a difficult thing to find, but I am considering an airplay or Bluetooth based solution.

5) Bluetooth: I have been unable to find a Wifi/Bluetooth combo half height card that will work so far, so I will have to go with a Bluetooth dongle.

6) The Optical Drive: Using this solution means using USB to SATA to connect to a drive, but it will still need to be powered.  May require 12V to 5V downconverter.

7) Power: Worst case Scenario would involve connecting AC to the small power brick that comes with the NUC, but this seems like a waste.  Unfortunately as this board needs 19V, either an upconverter or downconverter will be needed to go from either 12V or 24V.

Concluding Thoughts

Although I'm not certain, I am actually leaning towards this board,  If this was an i5, putting it on par with my previous system (with more RAM and better graphics) this would be a slamdunk.  Each EPIC or ECX board requires different connectors, drivers etc. As Intel is likely to continually upgrade this form factor, getting this right may "future proof" future designs.  I am likely to build this out and see what the final project looks like and how it functions.

 

I will certainly post detailed instructions and may do a video guide if there is enough interest.  Thanks again for reading!

 



The "Next Unit of Computing" - A Small Form Factor for Mainstream Users?

Courtesy of PC World

Pictured above is an all in one kit which contains a new Intel sponsored form factor called the NUC or "Next Unit of Computing" which if rumors are to be believed will go on sale this fall.  This little box features an Ivy Bridge Core i3 Processor, including HD 4000 graphics.

At 4" x 4" (102 x 102mm), the motherboard contained within is even slightly smaller than the smaller side of ECX boards (105 x 146mm - yes the 3.5" board is not actually 3.5", but it is the same size as 3.5" drives, which are not 3.5" but have 3.5" platters inside them).  These boards are smaller than the semi-mainstream nano itx boards (120 x 120mm) and even give the ultra-tiny PicoITX (100 x 72mm) a run for its money.

The only information I know comes from these articles:

Engadget's Story on the NUC

PC World's Story on the NUC

The Top of the NUC
(Courtesy of PC World)

But, if this is to believed, this would be a huge boon for hobbyists, modders, and small form factor enthusiasts.  To summarize, Intel undertook a project to determine the smallest possible form factor that would be needed to support a full Ivy Bridge CPU + Expansion and came up with NUC.  I had actually  read about this in an article several months back, but moved on when I read that intel sees this being used in digital signage and kiosks.  I thought that this was just a slightly different form factor for industrial/embedded applications that I've talked about many times on this blog (ECX, EPIC, etc).  I do not know if this was intel's goal from the beginning or if the popularity of other small form factors such as the Raspberry Pi, VIA's pico itx boards or Zotac's Zbox caused a change of heart, but it appears this product is headed for the mainstream.

The Bottom of the NUC
(Courtesy of PC World)

What makes the NUC board so special?

Now functionally, as of right now, there is likely little difference between the end result of using one of the industrial boards I have previously mentioned or VIA's/Zotac's offerings, and this board, but there are some key differences that make this board 'special'?

1) MAINSTREAM

What mainstream means is availability to consumers via retail outlets.  This may not seem like a huge concern, but take from someone who has desperately tried to get the latest small form factor boards from industrial/embedded companies.  The first question they ask me is how many employee's my company has followed by asking if the number of board I'll need is in the 10 - 100 board range or the over 100 range.  Being able to obtain 1 board with retail support is a huge bonus.  While this is overpriced at $400, at least that includes the entire kit including the case.  I would also expect this price tag to fall in future iterations.

2) INTEL INSIDE (and its IVY BRIDGE)

While the Raspberry Pi is great for Arduino Fans and other ARM processors are Android ready, Intel and the x86 architecture remains the most versatile chip available.  Capable of running almost any operating system and it seems to be in intel's best interest to keep its hardware as operating system agnostic as possible.

This board is designed to have the most powerful architecture on it.  Although available in more powerful varieties, most small form factor boards are power-sipping, ATOM or FUSION based.  Not so here.  Yes, it is only i3 to start, but i5/i7 variants are supposedly in the works. 

3) EXPANDABILITY

At first glance the few USB ports and HDMI may seem paltry, but the one word that makes all the difference is THUNDERBOLT.  The next generation interface will allow for devices to be daisy chained as if they were part of the board itself.  Think of this as attaching daughter boards, if you want more usb ports, more display interfaces, more storage, no problem.  But, its even more, the PCI express speeds allow for connection to graphics cards is the need arises.  This allows you to build a board in any orientation and with whatever components you choose around a 4" square core.

4) GOALS OF USE

Despite the fact that it works, ECX/EPIC Boards are not intended for consumer computing and contain features that are somewhat wasted.  From security features to direct LVDS connections to dual gigabit ethernet to the ability to support a SIM card.  These proprietary features are usually left unused and in some cases even have to be disabled to make the boards more compatible.

All in all, I hope this board is a sign of things to come.  This is obviously a niche product, but most OEM computer products are niche at this point, from LED enshrined gaming cases to water cooling components.  The point is I believe that there is a market for people who want to incorporate powerful systems into small products and locations.  The smaller it is, the more extensive the options are.  But, I have to admit, I think the NUC would look fantastic in the base of an iMac G4.

Classic Merit Megatouch meets Classic Apple

The Merit Megatouch Bar/Table Top Game Machine

The Merit Megatouch Maxx (Saphire)

Megatouch Force

Maybe its nostalgia, maybe its a truly great piece of software/hardware, but I have always loved these machines.  I remember vividly playing photohunt at a local dive bar at a time when touchscreen technology seemed quite futuristic.  With less processor power than an iphone and resistive touchscreen technology that connected via serial cable, its amazing that I still see these machines being used frequently in bars and taverns.

Merit Ion Megatouch
(Courtesy of Jester's Amusements)

While I don't really know much about the various product lines that Merit offered, I do know that the most common machines I saw were the CRT Merit Maxx (with its jewel themed updates) and the newer Megatouch Force.

I'm putting together a game room and a Merit Megatouch was something I hoped to incorporate right from the start.  At first I looked at the modern LCD versions (such as the Aurora or Ion Lines).  In my opinion, the prices were astoundingly high for the level of hardware.  When I looked at older machines in various conditions, I again saw very high prices and a ver slow depreciation.  This didn't bother me so much, as it gave me an excuse to DIY it and truly make it my own.  Unfortunately, I found out that Merit does not license its software.  Thus, the reason for the high prices is really the software as well as excellent customer support from Merit.

Choosing parts is also somewhat of a pain as Merit is very protective of its software (as is its right).  Buying individual parts requires making sure your hardware and physical security key matches up with the Merit supplied hard drives.  The best bet is to obtain a working machine with defective screen and/or in physical disrepair, but functional inside (easier said than done).

So here is the motherboard:

Megatouch XL with Maxx Diamond conversion

Its technically and old Megatouch XL that was upgraded to the Megatouch Maxx
I again want to point out (both for my own protection and to state a fact).  This is a native Merit board, HDD, I/O card, and security key (the object with the battery and tag in the lower left corner of the motherboard).  The AT power source is new and replaces a defective one.  This is in NO WAY a hacked board and there is absolutely NO use of cracked or stolen/pirated or otherwise altered software.  Instead this is a genuine Merit Megatouch with some working parts (motherboard, I/O, HDD) and some non-working/damaged parts (powersource, touchscreen, CRT, enclosure) that I am replacing with available alternatives.

Booting is slow, the fan is loud, but it works

There is something very rewarding about repurposing old hardware that is otherwise destined for the trash.  This is especially true with "classic" hardware.  While "classic" is obviously in the eye of the beholder and difficult to define, to me it means, "a device that performs its original function in such a manner that it can not or at least has not been significantly improved upon, even if that function is currently considered obsolete."  With the iMac G4, from a mechanical engineering perspective, it "did its job" perfectly.  It allowed for nearly effortless manipulation of an LCD monitor.  Thus, making it easy to have the LCD conform to all potentially desirable viewing heights, angles, and tilt.  New technology may eliminate the need to change viewing angle to make a screen readable (IPS).  It may/will replace the need for LCDs with superior and more customizable viewing technologies (ex holograms, project glass).  But, if your goal is to have an all in one computer with a 15 - 20" LCD screen viewed on a desk, I don't think it has ever gotten better than the iMac G4.  People who love classic cars would likely say the same thing about their passion.  Similarly, Merit has barely changed the formula and, even in the iPad age, can still sell its touch devices for thousands.  This is because these Megatouch Machines "do what they do" perfectly.  They play simple, entertaining touch games that are both nostalgic and timeless.

The 17" ELO 1715L

A 300 watt AT PSU was easy enough to find for a few dollars.  The touch screen was somewhat of a happy coincidence.  The original touch screen was a 3M and I actually found an old touchscreen controller for this device.  However, I also an old 17" 4:3 LCD touch monitor from ELO.  While I was fairly certain the VGA would scale up easily to 17" from the original 15" CRT, I did not know if the touch screen would work or if I could calibrate it for 17".  I had forgotten that this particular touch monitor had both a usb and serial port option for touch control (I was planning on getting a USB to serial adapter), but did not need it.  It seemed to work, but clearly needed calibration.

First run - Touchscreen not Calibrated

The Menu Control connected to Momentary switch

I need to thank "Dark Paladin" and his work with Merit Megatouches.  In his project, which can be found here:

http://home.comcast.net/~dark.paladin/megatouch/

He reveals the 4 important pins including the two grounds at the top left and second from left, as well as the setup pin (top right) and Touchscreen calibration pin (second from right on top).  Using a momentary switch to temporarily ground these switches will send you to the Setup and Touch Calibration Menus respectively.  His design is definitely worth a read to anyone considering a similar project.

Touch Screen Working ... Photo Hunt Time

Some issues such as I/O, Sound, and Quieting the fan still need working out.

But the first thing to consider is the permanent housing.  The motherboard is way too bid for the iMac G4 and too wide for the iMac G5.  However, the other white plastic desktop of the era I feel would make an ideal home.  I am referring to the 17" Flat CRT based eMac.  Elimination of the CRT will give plenty of room for the PSU, Motherboard, I/O and HDD.  Cooling mechanisms and air flow are already present in the chassis.  In addition, my current 4:3 17" LCD should fit perfectly.  Despite this transition, because the CRT in the eMax is actually flat, it should be indistinguishable from the outside.

The I/O hub can be fitted with the momentary switches and the existing on/off button can be used.  The existing front speakers seem perfect for this mod.

Broken eMac = Future Megatouch?

Although it is bulky, there is a classic look to it and it will allow for a single contained unit.  I have picked up the broken eMac seen above.  The front bezel needs repair or replacement, but it otherwise appears to be in good shape.

All in all, I think this will make a very fun project while I await small form factor Ivy Bridge Boards for my new Pro iMac G4 mod.

Please feel free to ask any questions and as always, thanks for reading.
TO BE CONTINUED ........

20" iMac G4 - The Native PSU

20" iMac G4 LCD powered only by Native PSU

The Native PSU is not enclosed.  Once it is plugged in, it is live.  Please use extreme caution with both the Power Source itself and its wires.  Keep any conductive objects away from the PSU and do not handle either the PSU itself or make changes to its wires while it is plugged in.  As always, proceed at your own risk.

Background

C5 receptacle
Courtesy of Wikipedia

From the onset of my 20" All-In-One Sandy Bridge mod, it was clear that the native PSU was not going to fit (from both a physical space perspective and a heat generating perspective).  It was either the optical drive or the native PSU.  I kept the optical drive and used a PICO PSU instead.  This put most of the physical bulk and heat generation on the outside of the mod in the form of a power brick.  However, I certainly understand the draw of using the native PSU. First, a modder likely alread has one, its right there in the iMac, no extra parts need to be purchased (the cost can be substantial as high wattage Pico PSUs cost around $150).  Secondly, there is no power brick, the rear plug would house a receptacle for the rounded, 3 pronged C5 plug of the native iMac G4.  Third, and most importantly is that it was designed to power this display.  Because of this it has a wattage greater than any PICO PSU (190 watts) and has a 24V line for the display, eliminating the need an up converter or separate 24V source.

20" iMac G4 Native PSU

Connected to AC C5 Recepticle

The problem, or so I thought, with the Native PSU has been that it can not be "jumped" in a conventional manner.  "Jumping" is a technique used in conventional ATX PSUs.  Grounding (connecting to a ground wire) a particular pin in the motherboard connector causes the PSU to "turn on" in the absence of a motherboard and the momentary switch that the mobo provides to turn the psu and subsequently the computer and internal devices on.  A few intrepid readers have let me know that they have had success "jumping" by supplying 5V to a particular pin in the motherboard connector.  I had thought of this PSU as a variation of an ATX PSU, with similar properties.  The problem I had envisioned using this solution is I figured a separate 5V source, in the form of a second PSU would be needed to give 5V to the native PSU in order to "turn on or jump" the native PSU.  While this may have allowed for a low wattage second PSU, because you still needed a different PSU, it somewhat defeats the purpose of using the native PSU.  I was mistaken, at least for the 20" PSU.  This is not how the native 20" PSU works at all.  I did initially have a working PSU for the 20" (Side note: The PSU seems to have the highest failure rate of any iMac G4 20" part and has been almost universally dead on every non-operational 20" iMac G4 I have obtained), so I purchased a known operational PSU.  The one I bought is green and like everything with these computers, I have seen variation in the PSUs even between the same size iMac.  So, I can not say for sure that all PSUs will work like this one.

How Does It Work

"Clip" Side

The PSU doesn't really need to be jumped at all.  It is "always on".  Looking at the motherboard connector, one side (that has the motherboard clip on it) has 4 yellow wires, then a blue, then yellow and red that go to the molex, and finally a green wire.  The other side (without the clip) has all Black Wires except for one White Wire.

"Non-Clip" Side

To be honest, this PSU confused the hell out of me and I believed I had a defective PSU initially.  It was the Molex connector here that really threw me off.  To test PSUs, I have a Molex powered fan that also lights up.  I attach this to a molex connector from the PSU.  When I turn on a PSU, I expect to hear the fan and see the LEDs turn on.  This fan (like most) uses 5V, so it really only connects to the 5V lead (Red Molex) and a ground.  No matter what I did, I could not get the fan to turn on.  Of course, I could have supplied the 5V directly to the pin the fan was connected to, but that seemed ridiculous.  In truth, 5V being supplied to this pin is likely what happens with the native PSU/Mobo setup.  It wasn't until I tested the voltage on one of the (non-Molex) Yellow wires that I realized that the PSU was in fact live as soon as it was plugged in and the Yellow lines have +12V DC on them.  This PSU appears to be a variation of a "12V only" PSU (with one notable exception).  12V only PSUs rely on the motherboard for the DC-DC downconversion and most modern ones have 5V and 3.3V rails.  12V only PSUs are usually PSUs for low power boards.  It appears that the PSU supplies the motherboard with 4 12V rails in the form of the 4 yellow(12V) and black(ground) wire pairs.  This is similar to using a PCI-E 8 pin power connector (or 2 P4 power connectors).  The molex power actually emerges FROM the motherboard, 12V directed from the PSU through the motherboard out to the yellow molex and the 5V a result of the motherboard down converting 12V to 5V and sending that through the Red 5V wire.  So when I hooked the fan up to the molex, without a motherboard, I was in essence hooking it up to nothing.  It is pretty obvious that the molex wires come from the connector and not the PSU at all.  Initially however, I thought these wires might interact with adjacent wires within the connector itself, but this is not the case.  That leaves the green/black and white/blue wire pairs.

Looking at the motherboard side

The Green Wire (only on the 20") likely represents the only DC-DC conversion that the PSU does itself.  And its an up conversion from 12V to 24V (Though this could also be generated by a separate transformation from the AC current).  The Black wire that it is paired with is simply a ground wire.  There is no voltage detected when you plug the PSUs AC Cable in.  This is because the motherboard "tells" the PSU to supply the 24V rail only when its on.  The motherboard does this by supplying a +5V current to the White Wire with the Blue Wire acting as the ground in this circuit.

The PSU Pinout:

ATX PSU Pinouts

Naming Convention of ATX PSUs numbers from Right to Left, Top then Bottom, looking at the open pins (motherboard side) of the connector while the clip is positioned on the bottom.  I will keep this same convention for the pin numbers I use for the iMac G4s native PSU.

20" iMac G4 PSU Pinout

The pin numbers are identified on each pin.  I have also divided the 16 pin connector into 4 colored zones.


Yellow Zone (Pins 1-4 & 9 - 12): These 4 yellows and 4 black wires are on as soon as you plug in the PSU.  Each of the 4 Yellows (9 - 12) has +12V DC and the Blacks (1 - 4) are their corresponding grounds.

Blue Zone (Pins 5 & 13): These 2 wires form a powered switch.  By supplying 5V+ to the White Wire (Pin #5) and grounding the Blue Wire (Pin #13) the PSU turns on Pin #16, the Green Wire.

Red Zone (Pins 6,7,14,15): These 4 wires were used by the iMac G4 to power the optical and hard drives via 2 molex connectors.  The 12V for the Yellow and the 5V for the Red and 2 Black Grounds came from the motherboard.  As these are simply a molex cable hooked up to nothing, you can ignore these wires.

Green Zone (Pins 8 & 16): +24V will be supplied by the PSU via the Green Wire (Pin  #16), which is required for the backlights, when 2 conditions are met: The PSU is plugged in and the White/Blue (Blue Zone) Wires are supplying 5V, turning the the "Switch" on.  Pin #8 is the Black Wire Ground for the backlights.

Applying this to the 20" iMac G4 Mod

This will only make sense if you are familiar with my more recent TMDS to DVI iMac G4 mods.  In this case knowledge of the 20" iMac G4 mod in particular is recommended.  Click the link below for details:

All in One 20" iMac G4 Sandy Bridge Mod

and the iMac G4 20" Inverter Pinout:

Updated iMac G4 20" Inverter Pinout

I used a PICO PSU for this mod.  The PICO PSU has 12V rails, 5V rails, and 3.3V rails (the 3.3V rail is not needed for this mod).  In addition, I used a 12V to 24V DC-DC Upconverter to get the 24V rail required for the monitor.  To replace the PICO PSU with the Native PSU you need the PSU to supply 5V, 12V, and 24V.  As the native PSU has 12V working as soon as you plug it in, we have our 12V rail.  As noted above, if you supply 5V to the Native PSU, a 24V rail will be turned on, so 24V is taken care of.  This leaves only the need for a 5V rail.  While 5V is not actually needed by either the LCD or the backlights itself, you would need 5V for any device that is molex or SATA powered.  This includes hard drives, fans, optical drives, and even touch screens.

There are 4 basic ways to get 5V, which one you choose depends largely on what you intend to use in the base.

1) Use a second PSU - a PICO PSU connected to the native PSU

A PICO PSU with rocker switch

Almost all PICO PSUs use 12V DC input (some have wide ranges in DC input).  Power it by hooking a 12V line from the native PSU to the DC power in (the white and black wires pictured that hook up to the connector for an external power brick).  As the native PSU gives you 12V DC already, you do not need a power brick.  You must "jump" the PICO PSU in some fashion, depending on what your intended iMac G4 mod is.  The Jump mechanism can be "always on" with a simple wire or "on/off" with a rocker switch (as pictured) to control power out from the PSU.

If you are using a motherboard in the base that requires an ATX Power connector, this is without a doubt the way to go.  You can plug this into the motherboard connector, without having to wire all sorts of adapters and converters, at a negligible loss of space.  Of course if its connected to an ATX mobo, the motherboard will jump it for you.  

If you are using this for an external monitor with peripherals (ex. dvd drive), you can use the requirement to "jump" this psu to your advantage.  You can put a rocker switch here that will allow you to turn off everything its connected to.  Remember the native PSU will be on as soon as you plug it in, by jumping this psu without a switch, it will also be on.  Thus, drives will be spinning, leds will be glowing etc whenever it is plugged in.  With a switch here you can turn the whole unit LCD and peripherals completely off.  Just remember, no matter what wattage PSU you get, these are not additive, they are connected in serial, so you are still limited by the overall wattage of the native PSU.  Also, you have to make sure that the wattage is adequate for anything you have connected "downstream" of PICO PSU.

The PICO PSU is probably the most flexible option as they are available with P4 connectors. molex connectors. SATA power connectors etc.  If you are not using an ATX motherboard, you could even use the power from the pins intended for the motherboard.  However its expensive and not needed if you use Option #2.  And if you aren't using peripherals requiring 5V - it is way overkill and you should use Option #4.   I'd even recommend hooking up the White PSU wire using #4 and using the 5V rail from the PICO PSU only for peripherals because #4 works the best for sleep/wake.

2) Use a small form factor mobo that uses 12V only for power (ex KEEX ECX boards)

Many small form factor boards including ECX boards use a P4 connector.  This is a 4 pinned connector (2x2) that uses 2 - 12V and 2 - Grounds.  As there are plenty of 12V rails available from the PSU, simply take your motherboard power connector and attach the 12V DC lines to the Yellow wires from the PSU and the Grounds to the Black PSU wires.  In the picture of my KEEX-6100 below, the P4 connector can be seen in the front right corner of the motherboard.  This connector attaches to a 12V rail from the native PSU.

The KEEX-6100

The reason this will work is that this board (as well as several other small form factor boards) works just like the original iMac G4 motherboard in that it requires only 12V in to work and it itself has downconverters on it.  The KEEX-6100 actually has a mini-Molex/SATA power out port, which can be seen in the back, just left of the fan.  This gives a couple molex out, including 5V.  So you have a 5V line from here.  However, as above, I'd still recommend hooking up the White PSU wire using #4 and using the 5V rail here for other peripherals as #4 works the best for sleep/wake.

3) Also a 12V to 5V downconverter can be used:

The PSU circuit

AC Plug into the wall is transformed into 12V DC by the PSU and plugged into the motherboard supplying 4 12V rails to the mobo.  When the power/momentary switch is pressed the motherboard turns itself on, opens gates to downconvert some 12V current to 5V.  Power is sent from from the motherboard to the 12V and 5V rails of the molex wire to supply the drives.  Also 5V is sent in a circuit back to the PSU via the white wire and back via the blue wire.  This turns on a transformer or up converter on the PSU which then sends 24V via the Green wire to the LCD.

This is actually quite brilliant and remarkably simple.  This opens up several intriguing possibilities for future mods.  My first test was to add 5V via white/blue from an AC to molex and confirm 24V on green/black with multimeter.  I did not want to add a second PSU and I knew power was technically already flowing to the 12V rails, I simply mimicked the motherboard using a very small, inexpensive 12V to 5V downconverter.

15W Downconverter

The PSU circuit and how I created it:

I cut free from the motherboard connector these wires: (The grounds are interchangeable, I used the matched pair across for convenience)

12 to 5V DC-DC downconverter hooked up

1 Yellow/Black (NON-MOLEX)
The White/Blue
The Green/Black

The Yellow was connected to 2 wires:
   The alligator wire the comes from the 12V LCD wires in the Gray Cable of the neck (Purple, Yellow, and Orange).  I also connected this to the 12V input of the Downconverter.
The Black was connected to the Gray Cable of the neck/LCDs grounds (Blue, Green, Gray, and Pin 15 of the DVI).  I also connected this to the ground input of the Downconverter

The White was connected to the +5V out of the downconverter and the Blue connected to the ground out of the downconverter.

The Green was connected to the inverter cables Red/Blue (+24V) and the Black to the inverter cables Green/Black (Ground).  Turn in on and there is the video.

Native PSU and LCD reunited

4) The Best and Easiest Way using the DVI 5V Pin

Overview

Really the best and the easiest way to do this especially, if you don't need a 5V rail for anything except for the LCD monitor is to use the 5V from the VEDID.  The is pin #14 on the DVI Connector itself.  5V is sent from this via the DVI source (ex the computer) to Pin #14.  This pin is intended to carry the 5V to the LCD panel via the Hot Pink/Red wire in the iMac's Gray LCD cable.  We are already splicing this 3 times so far.  One goes via the Hot Pink/Red Wire to the LCD as noted.  One goes to a 1Kohm Resistor to DVI Pin #16 (The Hot Plug Detect).  The third goes to a 6.8Kohm resistor then to the Yellow (?Wake from sleep wire) of the inverter cable.  By splicing this again we get 5V which can be sent via the White wire of the native PSU to turn the 24V line of the LCD on.  You can splice this anywhere along the line, I did it at the cable that comes to the Yellow wire of the inverter.  I connected an alligator wire to the White Wire of the PSU and hooked it up to the line going to the connection between that line and the 6.8Kohm resistor on the side before it passes through the resistor.  This seems to work beautifully and results in the screen going completely dark during sleep appropriately.  To be honest, I'm kind of blown away at how elegantly this works.

Now if you see 5V for anything else, you will need one of the above methods.  Meaning, use this for the LCD, but if you want to power a drive in the base DO NOT USE THIS SOURCE YOU WILL DAMAGE IT! You will need some type of downconverter, either a standalone or part of a motherboard as mentioned above.

This has gotten me to rethink LED backlighting and I may try adding the touchscreen in some fashion using the existing CCFL LCD.

It is amazing how the components of this decade old, little machine continue to amaze me.  Whether its the mechanical grace of the neck, the remarkable use of convection cooling, or now even a simple/elegant power supply solution for such a limited space, the iMac G4 is truly an inspired design.  To those working on the 17", I have posted information on that inverter which works in a similar fashion.

Thanks for reading!!!