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!!!

17" iMac G4 (1/1.25Ghz Neck) Video Tutorial

What you see here can be applied to the other iMac G4's, just use the correct pinout.  This is the first time I have ever done a mod in front of the camera and this was more difficult than I anticipated.  This was done live in real time (for the most part).  I sped through the portions that were simply repetition (such as stripping a wire or pushing out every last pin) and did cut very small portions (mostly because I felt I said or did something confusing).  I do apologize for frequently pulling out of the shot, its hard to work on a small item with a camera in-between you and the project itself.  I still believe this is useful to people who are better at visualizing than pinouts or snapshots.  Also, you can get a sense for the time this takes.  While soldering and stripping can take days, without the camera and explanation, I could have finished this in an hour.

There are a few highlights:

-  To make the extra wires I used the iMac's own ground pins.  This worked great and saves you having to buy an extra neck.  This is certainly the way I would recommend proceeding at this point.

-  Frustratingly, I have purchased a refurbished 17" 1ghz neck to use in this demonstration (as I did not have any more completely intact ones).  It did have some variation in that in the black lcd cable, one of the four wires in the black cable, the Red Wire was replaced with a Gray/Off White wire.  In addition all the the positive TMDS wires that emerge from the four wires that are usually Red, were also Gray/Off-White.  I have seem a random color variation in refurbished necks before, however, it was frustrating that for my demo, this one had more variation than I have seen before.  So just remember, for the black LCD cable Gray = Red.  And also be aware that this variation does exist.

- The final part that involves connecting the Red Inverter Wire to the VEDID/Pin 14 is very important because of the way we have it setup.  The inverter will not turn on appropriately unless this step is done.

-  When making the extra cables from the 3 ground wires with pins in the iMac's Gray Cable, I add one extra wire (a black wire I took and stripped from the iMac's fan cable).  The wire is not really necessary, you can hook the resistor directly to the other wires, but I feel that one extra wire not only makes it more secure, but also gives an extra area when we split again by adding the Red Invereter Cable.  Remember this actually becomes a 3 - way split with 1 split going to the LCD via the iMac's own Red/Hot Pink wire, 1 split going to a resistor then back to the DVI via Pin 16, the hot plug detect, and the final split going to the Red inverter wire.  So the extra wire allows us to kind of split once, then split again, as opposed to a direct 3 way split.

This has also been integrated into the blog, but here are all 9 parts together:


Part 1: Introduction and Parts List

Part 2: Completion of the Parts List

Part 3: Freeing the Inverter Wires

Part 4: Freeing the LCD Wires

Part 5: Hooking up and Testing the Inverter

Part 6: Connecting the Black LCD cable

Part 7: Powering the Gray LCD Cable

Part 8: Hooking up the Gray LCD Cable

Part 9: Finalizing the Inverter and Demonstration

Hope this helps and good luck.  Thanks for reading and watching!

Afterthoughts and Future Plans

20" iMac G4 and 20" iMac G5 (Apple Cinema Display LCD Controller Hack)
Connected  to External Mac Mini

Genuine 20" iMac G4 All-In-One Sandy Bridge Hackintosh

Above you see my two favorite 20" mods.  The one on top uses an LCD controller from an Apple Cinema Display for both the iMac G4 (though the iMac G4 uses its native inverter) and the iMac G5.  These are connected to an external Mac Mini.  Although somewhat more complex, the great thing about this method is its stability.  It is really an apple cinema display in the form of an iMac G4 and G5.  The extra room in the in the iMacs is not put to waste.  The iMac G4 houses a USB optical drive (replacing the missing one on the Mac Mini.  The iMac G5's iSight and Mic are converted to USB.  This has become one of my most frequently used computers.

The second picture is my latest All-In-One Sandy Bridge Hackinosh using an ECX board to run Mac OS Lion.  This is very much native and did not require any alteration to the neck or lcd.  The computer, DVD burner, SSD (running lion) and onboard Compact Flash (running Windows 8 Developer Preview) are all internal.  This was a tremendous amount of fun and will make a great all-in-one computer.

Obviously both these methods are viable and both have their advantages.  From the outside, they are indistinguishable from each other or a native iMac G4.  Of course, which ever method you use for the LCD is independent of what you connect it to.

iMac neck connected to Apple Cinema Display

My slightly older 3rd method, used the actual housing from an apple cinema display.  The few extra millimeters this gave allowed the use of the cinema displays inverter (I had previously not been able to get the 20" iMac's native inverter to work).  This method also allowed for the addition of a 20" touch screen.  However, I have retired this mod for a couple reasons.  First, while I thought this was an acceptable work around at the time, I much prefer the look of the true LCD housing.  Second, while the touch screen was great with the iMac's design, I did not love the only touch screen I was able to find in the now rare 20" 16:10 size.  This resistive touch screen was fairly accurate, but its surface was uncomfortable to touch and its glossy plastic surface detracted from the resolution of the LCD.  Third, as a resistive screen single touch was all it could do.

While I now have a functional upgraded replica, I still like the idea of adding additional functionality to the iMac G4 with a touch screen.  There are a couple options that are now available.  Some capacitive screens have become much more reasonably priced.  Although they were originally designed as single touch, new software may be able to make them function with gestures and at multitouch.  Another possibility is optical or IR touch.  Although the available optionals do not come in 20" 16:10, they possibly can be tweaked.

The downside is that the 20" capacitive screen will add too much weight and the optical touch will require extra room between the LCD and the bezel.  One thing that may make this possible is to use LED backlighting which would be much thinner.  A fellow modder JP7 has done a fe amazing mods of apple cinema displays using LED backlights.

In terms of the base, I have no use for either a desktop monitor or an all-in-one.  But, a larger screen for a notebook computer has always been something I have considered for the iMac G4.  Using either wired technology (A thunderbolt dock? - If they eventually come in at a reasonable price) or wireless technology (Wireless DVI and USB adapter?) is something I can definitely see being useful.

Wireless DVI - Courtesy of Amazon.com

After I use my current G4 and G5 spare parts, I will probably move on from this.  And I still have a Cube which has been sitting waiting to be modded.

Inverter Frustration

After success with the 17" I was hoping good fortune would carry over to the 20" mod.  However, the 20" Inverter has continued to be a problem.  As the DVI/TMDS is essentially the same as the 17" (with just extra power to the panel) I don't anticipate this being a problem.  So the task of turning on the backlights seems simple enough.  Here are the problems and failed solutions I have tried:

The original inverter is remarkably flat  and specifically designed to fit in the monitor chassis. I have not been able to get consistent even lighting.  It does require a 24V line so I am using a separate DC line to power the 2 24V lines. As you can see I have gotten some response.  By giving 12V to the on/off it can become very bright.  But, this is neither stable nor even.  Without a doubt there is some way of mimicking the iMac's signal and use the native inverter.  But, I am not an electrical engineer and the entire purpose is to keep this as simple and stable as possible.  I have thus moved on in an attempt to find another solution.



Aftermarket inverter.  Available on ebay are several relatively cheap universal inverters that can support 6 ccfl lamps with a 4pin and 2 pin connectors.  This one was $30.  I'm not sure if the picture does it justice with the glare, but the screen is evenly lit and bright.  Whats more is that the connections are very simple.  There are two 12V rails, 2 grounds, one on/off - which takes 5V, and an adj/dimmer.  However, while much narrower, it is longer and more troubling, slightly thicker than the native iMac G4 inverter.


I thought it may be possible to make it fit in the case with some alteration using a multi-max dremel.  The back of the monitor housing uses "raised x's fit the monitor tightly.  I thought that by removing these raised areas I may be able to create a little more room for the thickness of the inverter.  As you can see below on one side the "Raised X" has been removed and sanded down (this does not damage the back or outward appearance at all).  I then placed the inverter in at several angles (to try I didn't use the protective plastic covering).

 As you can see it just doesn't fit .  I don't want to press down firmly, screw it in, and leave it under pressure.  I know it may not look like much but it extends around the entire side of the monitor.  As I was hoping to make this a touch screen as well, the monitor is likely to be somewhat unstable in the housing.  So I looked for other 6ccfl inverters that may be slightly thinner.

 Here are 5 inverters that are designed for 6ccfl monitors.  From top to bottom: an iMac G5 inverter, aftermarket on ebay (4pin/2pin), aftermarket on ebay (2pin x 3), a 20" apple cinema display inverter, and the aftermarket inverter used above.  The only one that the case would close with (even with the dremel modification) was the cinema display inverter.  However, it still took a little force and unlike every other inverter pictured, this is not a straightforward inverter (there are actually 8 pins - more than the iMac).

 I had also thought about using LED lighting (which does not require an inverter) however after a brief test of constructing my own led rail, I was not happy with the results (uneven lighting).  Putting the iMac's LCD onto a commercially manufactured  20" LED backlit montitor would likely work very well.  However, they simply do not manufacture 20" LED backlit LCD's in the 16:10 (1600x1050) orientation, which would be required for this mod.

So, I am left with 2 options: Continue to search for a solution to the 20" backlighting problem or to complete the all in one mod using the already built 17' monitor assembly.  I do have another idea for the 20", so I am not giving up yet.  After using my previous 17" mod for sometime, I do have to concede that a 17" monitor seems awfully small these days and a 20" would be preferable.  Plus, I have located a 5 wire resistive 20" touchscreen which would be ideal for this mod.  If anyone has any ideas, tips, or suggestions, they would certainly be appreciated.

The Elusive All-In-One

Let me introduce you to my new favorite form factor: The Embedded Compact or ECX.  When I took this out of its box, even though I knew its dimensions, I was shocked at how small it was.  I do want to caution that everything with these boards is proprietary including its cables and proprietary = expensive.  So know what your getting yourself into.  I've seen these available in either Atom or most excitingly Mobile Core 2 Duo configurations as this one is.

For perspective I have included a picture with a metro card (credit card sized).  To demonstrate how small these boards are.  The have the same dimensions as a 3.5" drive, but they are also quite thin as the mobile processor fans are small and the ram inserts horizontally on the underside of the board.

In terms of features you can see the PCIe x 4 slot, a DVI/VGA/HDMI out.  However, there is actually an LVDS out as well inverter pins (yes the entire LCD conroller is embedded in this tiny motherboard).  So you could connect the LVDS cable and inverter directly to this motherboard without any additional hardware.  Now the question is can the native LVDS resolution drive the iMac's 20" screen? And does this solve the problem with the inverter for the 20" iMac - maybe?

The underside shows the RAM (4GB) in place (purchased separately) as well as a slot for a Compact Flash Card.  This I also find to be a fantastic addition.  I need all the space I can get and although I am not sure, I would be surprised is an embedded board was unable to boot from the compact flash memory. This could mean with a 64+gb card no need for a hard drive, no extra heat or power, and a much faster system.


Here is the 2.53 Ghz Core 2 Duo Mobile (Socket P Penryn Processor) and its very reasonably sized heat sink/fan.

This is the first board that I have felt makes an all-in-one doable.  I have never liked the idea of shoehorning a mini itx or mac mini into the base at an angle.  Plus I had extreme concerns about airflow.  I imagine this sitting above the dvd drive with the cpu fan around the same place as the iMacs original fan.  This board also allows incorporation of a dvd drive.  Although not necessary anymore, I always felt it was part of the iMac's charm.  In addition, if no other hardware is required that would leave the bottom for placement of a powerwave adapter (to use the original speakers) as well as extenders/ports to make the rear I/O look as original/professional as possible.  It does use a power brick, but I am certainly ok with that as no internal powersource = less heat.
Now I could find this board impossible to work with, it may not fit at the top of the base, it may require a hard drive.  I don't know, but keep this in mind the original iMac was an embedded compact motherboard, it only makes sense to use something along those lines.

I already know I can thread LVDS cables down the neck into the base with a replacement 20" LCD.  However, I could also try to splice the existing panel to DVI.  I'm not sure which way I'm going to go - but I am leaning towards LVDS (if the native resolution is compatible) as it is embedded onto the motherboard, thus will turn on/off with the motherboard etc.  For people interested in doing this, you will need extra LVDS cable.  The best place to get it is ebay.  I find cables used in flat screen tvs are usually longer and of more use.  Examples of LVDS cables from tvs are shown in the pic on the right.

The biggest problem I'm going to have is with that damn 20" inverter (I am not running high voltage cables through the neck again - too unsafe).  Unlike the 15 and 17" I have not been able to get it to work independently.  Although there are pins for the inverter on the motherboard, it is one short.  I believe there is some voltage difference involving orange and yellow that turns the inverter on.  I am hopeful that maybe by having an active dimmer hooked up that this may solve the problem.  Obviously using the native inverter with the motherboard would be option number 1.

Option 2 would be to locate some other aftermarket inverter that will work.  I have yet to find one that is "flat" enough to fit in the monitor casing, but I haven't looked for sometime.

Option 3 is something I have recently begun to play around with and that is led lighting.  I could try edge lighting the lcd glass, replacing the CCFLs with these superbright leds from environmental lights.  These work on a 12v dc line which can be supplied directly from the motherboard without need for an inverter.  This is a 6 foot roll.  They do come brighter however, this requires a 24v dc line.  If this is not bright enough, I may try led back lighting instead of edge lighting.

Option 4 is using the 17".  Although I'd prefer the 20", if getting the backlights to work on the 20" proves too difficult, I already know how to do so with the 17".  And would be quite happy with a fully all-in-one modernized 17" iMac G4.

I'd love to hear advice from people who have some know how with led backlights etc.  And as always I'd be happy to answer any questions.