Sunday, November 13, 2011

All-In-One 20" iMac G4 "Genuine" TMDS to DVI Mod - Completed (With Guide)

iMac G4 running Lion
As I noted earlier, two newer developments helped with figuring out how to turn on the inverter.  For one, the apple cinema display controller worked with the inverter.  Although this arrangement clearly differed from how the inverter is natively controlled and required an extra wire for sleep function, it allowed me to at least have an idea of the voltages of each wire.  Secondly, using the DVI connector that I discuss in my 17" Guide, I can reliably create a DVI connection for the LCD in 10 minutes.  Before this required cutting soldering, and permanent alteration of the wires and pins.  As such, it wasn't long before the inverter was turning on the backlights.  In fact, the solution was not complicated, I have no idea how I didn't just stumble upon it.  The only special requirements are a 24V line in which there are two solutions I have that both work fine.  I would imagine it is possible to use the native power supply, but I have been told that it can not be "jumped" in standard fashion.

I do want to mention that there are definitely more sophisticated solutions.  In fact, its unlikely that I'll even add dimming and to get the monitor to sleep I'm currently using somewhat of a trick.  There are several people that are using this foundation to do very impressive things and I can not wait to see the results.  What I am attempting to do is create a DIY solution that is both cheap and reliable, but above all is something that can be replicated by someone who has limited technical skill.  Such as the ability to wire up a multi speaker AV receiver and can build a computer from off the shelf components purchased from a store like newegg.  That said, this is not the definitive word, for those with more knowledge and skill, improvements and suggestions will be welcomed.

I will not focus on pinouts in as detailed a manner as I did in my 17" Step by Step Guide.  The guide is essentially the same.  The only differences are in a few pin numbers.  Just use the pinout above as your guide if you need help.  What I will spend more time on is the finalization.  How to stabilize the mod as best as possible and how to put it together, not just as a DVI receptacle in the base but as a sandy bridge updated all in one.  To do this I'll be using the previously mentioned KEEX-6100.
KEEX - 6100 ECX (3.5" board)

This board or several other ECX boards can be obtained from

Here is their selection of ECX boards

They can help you out with all needed accessory cables as well.  The customer service has been fantastic and I highly recommend Sliger to anyone looking for an ECX board.

This is a fantastic board and whats more is that I can now confirm that this board is indeed "hackintoshable" using a retail/vanilla installation with appropriate boot loader.

I. Power Source
Updated (5/8/12): The original 20" PSU can be used to power the LCD and a computer in the base without use of a second power source.  Detailed below are 3 different methods to power the LCD +/- computer in the base.  The first, using the native PSU and 5V that is provided by your image source via the DVI cable to DVI Pin #14.  Note that this 5V source of power is spliced several times during this mod for various reasons.  The second uses an external power brick that transforms 120VAC to 24VDC then splits to a PICO PSU that accepts the 24V and to supply the 24V to the backlights.  The third uses an external power brick that transforms 120VAC to 12VDC then to a PICO PSU that accepts 12V and a 12V to 24V DC up converter to get the 24V line for the backlights.  All methods work, but the native PSU does not work with this design.  The KEEX 6100 can not fit above the drive with the native PSU.  If you remove the optical drive, you can then lower the mobo and keep the native PSU (This is the preliminary design included in my upcoming "20" iMac G4 Pro Mod").  For this design I went with the third method.

A) The Native 20" PSU

Using the Native PSU alone
Several readers have used the original PSU with success.  Although the original PSU does not fit in this mod, I decided to give it a try.  The original PSU appears to be a 12V only (with one exception) which relies on the motherboard for downconversion to 5V.  The 20" motherboard does two major things with the 5V.  For one, it supplies 5V to the molex cables to power the optical and hard drives.  The second thing is to give 5V back to the PSU in the form of the White Wire(+) and Blue Wire(-) which turns on an up converter or transformer which gives a 24V line (Green Wire and Black/Ground) which powers the monitor.  Initially I was not a fan of this idea because I was under the impression that the White/Blue 5V "jumped" the PSU, so a 5V current was needed from a second PSU in order to turn on the native PSU.  However, the native PSU is on once it is plugged in, so you can use its own current to get the 5V, hook it to a motherboard that needs only 12V and can down convert to 5V (such as the KEEX ECX Boards), or if you don't have any additional needs for 5V except for turning on the power to the LCD's backlights, you can splice the 5V for the incoming DVI.

This method was not used for this mod, but for those interested much more detail is available in this post: 20" iMac G4 - The Native PSU

Briefly, to use its own current a 12V to 5V DC-DC downconverter (<$5) can be used to generate a 5V rail for devices and/or activation of the 24V rail.
12V to 5V DC-DC Downconverter

Also, to activate the 24V rail, you can use the 5V that comes in from your DVI source at Pin #14 as noted.  This is probably the easiest and most effective method.  Just note that this 5V is for turning on the 24V rail and for other purposes described later, do not use this as a 5V rail for devices such as drives as you can overtax and even damage your DVI source.  This method is best rewired in at the end of the mod when everything is hooked up.  Simply take the White wire of the native PSU and connect this to a splice of the incoming wire of DVI Pin #14: The VEDID which has 5V supplied by the incoming video signal.  (Note: Using this method will result in this Pin being split into 4 total wires).  But, do not use this pin to power any peripherals or devices as this may damage not just this mod, but your source (i.e. computer) as well.

Native PSU ONLY - 20" Power Scheme
As the original PSU will not fit in this design which uses the optical drive, the first decision to make is how can we power this in a different, but simple way.  By simple I mean - 1 plug, 1 power brick, 1 on/off switch.  This is actually a bit of a challenge because we not only need to power the LCD, but a Core i series mobo and processor, a 5.25" optical drive, and a HDD or SSD.  This will require something with a decent amount of wattage.  Whats more, the inverter requires 24V DC, the maximum voltage in a standard atx psu is 12V DC.  An ATX psu and all variations (flex, mini etc) simply take up too much room.  A picoATX psu is tiny as it uses an external power brick for AC-DC conversion, but the highest wattage I've seen is 150 - 160 watts.   So really there are 2 choices.  Convert from 120VAC to 24VDC and get a PSU that can handle that or go from 120VAC to 12VDC, get a standard PSU, but then up convert from 12V to 24V.  Again, a third possibility is the native power source, but this doesn't quite fit my design plans, so I will not be pursuing this method.

B) Convert AC Power to 24VDC
24V Power Scheme
AC to 24V DC Brick
I apologize about the crudeness of the above sketch as it is my original notes/design.
To Sum Up:

 An AC to 24V Power Brick is used (in this case the 65W Apple Cinema Dispay's Powerbrick).  I split the 24V DC OUT and Ground.  One part of the split goes to power the inverter, with the 24V connecting to the Red and Blue Inverter wires, and the Ground connecting to the Green and Black Inverter wires.  The other half of the split goes to power a Pico Power Supply Unit.

Variable input Pico PSU
This particular Pico PSU is 65watts and is a "variable" power supply.  This means that it can accept 12 - 24V DC INCOMING and it outputs standard tax voltages.  It has molex and sata power connectors.  The green alligator clips you see in this picture are connected to a rocker switch which I am using to "jump" the pico power supply.

The molex is used to power the LCD which has 3 wires (Purple, Yellow, and Orange) inside the Gray LCD cable which connect to the Yellow Molex wire - the 12V.  Unlike the 17" LCD which requires only 3.3V or 5V, the 20" needs 12V.  The iMac's Gray LCD cable also contains 3 wires which are o be connected to the black molex, the ground.  These are the Grey, Blue, Green wires.

The Purple wire I originally hooked up to 5V Molex, however, it does not seem to play any significant role in this setup and can be left floating.  The Orange wire, likewise, I left floating (it functions as a dimmer, I may try to get brightness working later).  The Yellow is the on/off, which requires a very small voltage.  A 1Kohm resistor works, but I went for an even higher resistor a 6.8Kohm which for testing purposes I hooked up to the red molex (5V), but will eventually hook up to the VEDID.  The reason for hooking up to the VEDID is so the backlights turn off when the led itself is told to sleep.

This method has a few disadvantages however, the 24V backlights are being fed voltage essentially outside of the "control" of the Pico PSU.  As such the rocker switch does not turn off all power going into the computer.  In addition, the 24V power bricks are less common.  The biggest disadvantage however is the available PSU wattage.  The most powerful Pico PSUs I was able to find require 12V DC incoming.  As I plan on making this a Core i/Sandy Bridge all-in-one and 40 or so watts are required for the 20" LCD alone, every watt counts.  So while this method works, I decided to pursue a different approach noted below.

C) Convert AC to 12V then Upconvert to 24V

The largest pico PSU I was able to find was the 160watt PicoXT.  It comes with an admittedly large power brick, but 160 watts should suffice for both the motherboard and the display.  This should eliminate the need for multiple power bricks.  Also, all power flows through this PSU.  In the PSU picture, you can see how the "jump pins" are connected to a rocker switch.  This gives me a hardware, full power off, on the machine.  In addition, the PSU has some useful connectors.  There is a molex (needed for the LCD), a SATA Power (needed for the SSD and DVD drive), and a 4pin CPU connector.  Conveniently, the ECX board this 4pin connector for power.  This particular model also has a convenient external plug, which I will show later in the mod.

As we are starting with 12V DC and the inverter needs 24V, the only way to get the needed voltage is to use an upconverter.  Pictured here is a very reasonably priced 72watt DC-DC converter.  This outputs 24V at 3A which is enough to power the inverter.

DC-DC 12V to 24V Converter
Although it has a somewhat unusual shape, it appears that I will be able to incorporate it into the side of the optical drive cage.  This is simple to use.  Connect the Yellow and Black (12V and Ground) of the molex to the Input and then hook up the 24V and Ground Output to the inverter wires.  The Red and Blue inverter wires connect to the 24V Out and the Green a Black inverter wires connect to the Ground Out.

Otherwise the schematic is the same as above.  The yellow wire remains connected to any resistor of at least 1Kohm (I used 6.8 Kohm) and then to 5V for testing and eventually the VEDID.

Make sure you test this out before proceeding.  The backlight should visibly turn on, it won't be a blinding light, but you should clearly be able tell when it is on or off despite ambient light.

So here is the inverter pinout including the 12V to 24V DC-DC Upconverter, which is the method I currently recommend:

20" iMac G4 Inverter Pinout
And here is the new scheme using this method:
12V to 24V Power Scheme


iMac G4 20" TMDS to DVI Pinout
DVI Connector

I will show every important step but will not be going into quite as much detail as in my 17" guide.  The principal is exactly the same, but the pinout (which pin plugs where) is different.  Again this method utilizes a special DVI connector that fits into the iMac G4's LCD pins perfectly.

Pictured here is the DVI connector that makes this mod possible.  For details on this connector please see this post: DVI Connector Method.

Female DVI Pin Number from Tom's Hardware
 The TMDS to DVI Pinout shown above has four columns.  The 1st column (left to right) refers to the the cable that plugs into the iMac's LCD at the top of the neck.  As we are not opening the LCD this is not really relevant here.  The second column is the color of the wire that comes out of the iMacs neck.  The ones that say "xxxx to yyyy" are the cables that come from the Black Cable in the neck.  The "single" colors come from the Gray Cable in the neck.  The 3rd column is the function and the 4th/rightmost column is the DVI pin number.  It is this column that refers to the location/pin on the FEMALE DVI Connector.

Remember, this pinout refers to the FEMALE connector only.  In reference to our connector the pin numbers are shown to the left.  The iMac's LCD is Digital Only.  DVI can have both digital and analog areas.  This connector is digital only.  There is a horizontal slit where the analog pins would have been.  I refer to this as the "Analog Area" and it is for orientation purposes only.

Although we know the pin number from the front, this is a right angle connector.  So we have to "trace" the pins and identify them on the bottom of the connector.
The pins make a 90 degree turn

The Most Important View - The Bottom Pins
Looking from the Bottom, The Top Row ends up at the back, the Middle Row in the middle, and the Bottom Row closest to the front.  This is where the female pins of the iMac's neck cables plug in and thus the most important view.  Using this view and columns 2 and 4 in the TMDS to DVI pinout you have all you need to complete this.  Take the color from column 2 and plug it into the numbered pin pictured above identified by column 4.

A) The LCD cables

Left of the connector you can see the iMacs LCD cable.  Originally this comes in a connector that plugs into the motherboard.  Using a flat head screwdriver and safety pin, you must free the individuals pins from the connector until they are all free as pictured.  DO NOT REMOVE OR DAMAGE THE PINS AT THE END OF THE WIRES.  Take your time and be gentile.

For the iMacs LCD cable you must first remove the metal casing using a flat head screwdriver or x-acto knife.

- First pry open the top
- Then the side
- And then the metal cover should bend back and snap off

When the black is fully exposed you will again see little plastic tabs on the side.  Using a safety pin lift these tabs and push them down (its ok if they come off entirely).  You want to see the exposed metal from the pins where the tabs used to be.  Do this for all the tabs on both sides of the cable.

When all tabs are done, VERY GENTLY pull the individual wires and pins free.  This should not require any force, the pin should easily slide out.

If there is any resistance, then you may need to again use your safety pin to press down on the pin in the area where the tab used to be in order to help free it from the black connector.  Usually once you push it down a little the pin will become "unstuck" and then will be able to be removed without difficulty.

Although not required, I have found it helpful to cut the tape that holds the Gray and Black cables together allowing the two cable to be manipulated individually.  Once both cables with its pins intact are free you can begin hooking them up to the DVI connector.

B) The DVI Connector - Black Cable

 LOCATE PINS 1, 2, and 3 on the DVI.
   - Closest Row to the back of the connector
   - Furthest from the Analog Area
   - Find the iMacs Black Cable and isolate the Brown Wire
   - Take the Green Wire in the Brown Wire and Press it into PIN#1
   - Take the Red Wire in the Brown Wire and Press it into PIN#2
   - Take the Black Wire/Shield in the Brown Wire and Press it into PIN#3

LOCATE PINS 9, 10, and 11 on the DVI.
 - Middle Row: Directly in front of the Brown Wires Just Placed
 - Furthest from the Analog Area
 - Find the iMacs Black Cable and isolate the Blue Wire
 - Take the Green Wire in the Blue Wire and Press it into PIN#9
 - Take the Red Wire in the Blue Wire and Press it into PIN#10
 - Take the Black Wire/Shield in the Blue Wire and Press it into PIN#11

LOCATE PINS 17, 18, and 19 on the DVI.
 - Closest Row to front: Directly in front of the Blue Wires Just Placed
 - Furthest from the Analog Area
 - Find the iMacs Black Cable and isolate the Green Wire
 - Take the Green Wire in the Green Wire and Press it into PIN#17
 - Take the Red Wire in the Green Wire and Press it into PIN#18
 - Take the Black Wire/Shield in the Green Wire and Press into PIN#19 

LOCATE PINS 22, 23, and 24 on the DVI.
 - Closest Row to front: Same row as the Green Wires Just Placed, however at the other end.
-  Closest to the Analog Area
 - Find the iMacs Black Cable and isolate the Red Wire
 - Take the Green Wire in the Red Wire and Press it into PIN#24
 - Take the Red Wire in the Red Wire and Press it into PIN#23
 - Take the Black Wire/Shield in the Red Wire and Press into PIN#22
 - ***Notice that the wires are placed differently here, from left to right it goes Black, Red, Green, which is the reverse of the previous placement.  One way to confirm is to make sure the small Green wire is always on the outside, the red wire in the middle, and the shield/black wire should be the "innermost" wire.

Here is a summary picture showing where each wire should go:

For now focus only on the black LCD cable.

As Shown, The Black cable gives off 4 wires:


Each of these is composed of 3 subwires, a Negative, Positive and shield.  These are the small Green, Red, and Black wires respectively.

Please confirm that what you have matches this illustration.

C) The DVI Connector - The Gray Cable

There are a total of 9 wires in the Gray Cable, only 3 of these hook directly up to the DVI Connector.  The other 6 are used for powering the LCD (3 cables for Grounds and 3 cables go to 12V)

So 3 wires go to 12V - This is the Yellow Molex Wire
-  For those familiar with the 17" mod please note that this represents a substantial voltage change.  (3.3V or 5V to 12V)
-  I am using alligator clips for now but will replace this with actual wire later.
-  The 12V wires are the PURPLE, ORANGE and YELLOW

3 wires will go to the ground wire - This is the Black Molex Wire
- The Ground Wires are the GRAY, BLUE, and GREEN

12V and GroundWires
3 wires remain, these will hook up to the DVI Connector
-  2 wires (WHITE and BLACK) are straight forward.  Go ahead and hook these up.  The Black wire's pin pushes into DVI#6 and The White wire's pin pushes into DVI#7.  The final pin in this row #8 is left unconnected.  
-  1 wire (RED - has somewhat of a "hot pink" hue) is more complex as its needed for 2 purposes.  One is to plug into pin #14 - but a modification must be made first.

D) The DVI Connector - Create our own cable.

The reasoning for this is explained in my 17" Guide, so I will not get into it here.  Suffice to say that a small amount of voltage is required to feed back from the LCD to the DVI source.  The iMac does not provide this (it was an all-in-one, so was not designed to detect when its own monitor was plugged in).  We will work around this by feeding the DVI connector its own voltage right back to itself.  This is called the Hot Plug Detect.  In addition an extra DVI to ground is needed.

What is needed? 4 wires of a similar gauge to what is found in the iMac's Gray LCD cable.  A 24 - 28 Gauge will probably suffice.  However, 3 of these wires should include female pins.  The easiest source of such cables is an extra iMac Neck (of any size).   As they include the correct size of pin, this would be the easiest.  However, alternatives include LVDS wires, as well as unused wires in the iMac itself such as the fan wires, the internal speaker wires etc.  You do not need long wires at all.  You could probably get by with each being about 6 - 10cm or so.

The most important thing is to make sure things are well secured and to do this, you really need the proper pins.  While I used wires from an extra iMac neck, I just realized for those without an extra neck, there is a great source of extra pins and even wires staring right at you:

     The iMac's Gray LCD cable's 12V (ORANGE, YELLOW, and PURPLE) and GROUND (BLUE, GRAY, and GREEN) wires.  Unlike the very difficult to work with wires in the black cable, these are much easier to strip and manipulate.  What's more is that these are not signaling wires, so a less than perfect hook-up will not cause any distortion of your image.  These wires are not plugging into the DVI connector so the pins are superfluous.

I still recommend using the wires from an extra neck if you have it as once a wire is cut there is no going back, but this is certainly a viable alternative.

So either:
A) Cut 3 or 4 wires from an extra iMac G4 neck (about same gauge as wire in Gray iMac LCD cable).  3 of these wires should have the female pins that connect to the DVI Connector (about 10cm).  And one other similar gauge wire (can be shorter), with a male pin if possible, but definitely not a necessity.  I will refer to this last wire as the "Extra" wire.

3 Cables from extra iMac neck Gray cable (Green, Orange, Yellow)
and 1 White LVDS wire with a male pin on its end


B) Peel back the Gray LCD cable's Plastic and Shielding about 16cm.  Isolate the Ground Wires: BLUE, GREEN, and GRAY. (You can use the 12V wires as well, but I would feel safer cutting the grounds).  Cut these three wires at about 10 - 12cm).  Make sure you leave enough wire remaining so that the remaining ends can be easily stripped.

*Note these pics reflect an extra damaged iMac cable I had.  I had this idea too late for this mod, but I will use this method for my 17" 1/1.25 Ghz Guide.

Plastic and Shielding Peeled Back
Take the now cut ends of the BLUE, GREEN, and GRAY wires in the Gray LCD cable and strip the last few centimeters of each of these wires so that each now has exposed wire at the end.  Twist these 3 wires together.  You can now hook this up to an alligator wire or a different wire and hook it back up to the black Molex/ground.

The 4th or "Extra" wire can really come from anywhere, if you do not have any other small gauge wires, you could cut 1/3 of the non-pin ends of one of the wires you just cut.  Or just take one of the fan wires or internal speaker wires etc. that are not being used in the iMac's casing.

1.  The First wire - I used a GREEN Wire, with female pin, the Ground
- Strip the non pin end of this wire
-  Push the female pin of this wire into DVI Pin #15
-  Take the stripped end of the wire and wrap it with the other ground wires from the iMac's gray LCD cable.  Either wrap it around the pins or twist it into the the stripped wires the you just cut.  So this wire should join with the BLUE, GRAY, and GREEN wires from the Gray LCD Cable and connect to the Molex's ground/Black wire.

2.  The Second wire - I used an ORANGE Wire, with female pin, the VEDID
- Strip a large portion off the non pin end of the wire (a good 4cm)
-  Take your "Extra" wire - Mine is white - and strip one end.  If it has a pin strip the non-pin end.  If it has no pins, strip both ends.  

Second wire [Orange - Bottom Right] with "Extra" Wire
[White - Bottom Left] coming off and remaining stripped wire seen on top

- Wrap the stripped end of the "Extra" Wire around the Second wire's strip.  But do this at the very beginning of the strip. close to were the plastic covering resumes.  So your wire should look like above with a large part of the second wire's exposed wire still coming out.

3.  Take a 1 Kohm resistor and connect it to the remaining exposed wire from the second wire

With Resistor Added
4.  Take your third wire - I used a YELLOW wire and strip the non-pin end.  Wrap this wire around the other end of the 1 Kohm Resistor

5.  Secure the resistor with electrical tape +/- solder

6.  Connect the 3 ends of your newly constructed cable
-  The second wire (ORANGE) has a female pin that should be pushed into DVI PIN#14
-  The third wire (YELLOW) has a female pin that should be pushed into DVI PIN #16

-  The "Extra" wire (WHITE) has either a male pin or stripped end.  This should connect to or wrap around the Red (Hot Pink) Wire's Pin from the iMac's Gray LCD Cable.  Leave this connection exposed or at least accessible, as we will eventually add something to it.

Hot Pink/Red Wire Interface

- What we've done is create a cable that takes the voltage from Pin #14 and splits.  One split continues unaltered (Orange Cable to White Cable) and connects to the Red/Hot Pink wire as it was intended.  However, the other split runs the voltage from Pin #14 through a resistor and then gives the reduced voltage back to Pin #16 (Yellow Cable) - The Hot Plug Detect.

7.  Controlling the Inverter.  The final thing I recommend doing is to connect the Yellow Wire of the Inverter (the on/off) NOTE: I DO NOT MEAN THE  YELLOW CABLE I USED ABOVE.  to the Hot Pink Wire, the VEDID.  Leave the Yellow wire hooked up to the "at least 1 Kohm resistor" (I used a 6.8Kohm, but tested it with a 1Kohm which worked, though 6.8Kohm better approximates the original signal, but use an extra wire - I used a green wire, to connect to the Hot Pink/Red Wire Interface above.  I simply stripped the wire and wrapped it around.  This is optional, but whats nice about this is that the backlights will turn on and off with the signal it gets from a computer, instead of having to turn the backlights on and off seperately.

8. Test your signal.  Hook the DVI up to a working computer capable of displaying graphical images (no just a boot screen).  Look at the picture closely, look for color distortion or red/green flickering dots.  Color distortion may indicate something hooked up wrong, dots flickering indicate crosstalk.  Remember TMDS uses very slight variations in voltage between the wires to determine what gets output.  If there is a nearby wire with relatively high voltage it may "communicate" with a nearby pin.  Make sure the pins haven't bent  and are spaced apart and consider even adding tiny pieces of electrical tape around pins.  (Especially the small Red/Green/Shield Pins that are near pins the carry voltage.  Make sure your image is pristine before continuing.

9. Replace the Alligator Wires.  Assuming everything works, its time to use extra wire (18 to 24 gauge) to replace the alligator wires (technically you could cut the alligator wires themselves, but this would waste them).  I recommend soldering stripping the wires, wrapping the wires around the pins, soldering them and using either heatshrink and a heat gun or electrical tape to secure them.

10. Secure your wire.  Solder only if you are an expert, its very easy to solder nearby pins together.  Instead I used a great insulator - hot glue.  After using some electrical tape I coated the wires and pins in the back of the connector in hot glue using a hot glue gun.  This is secure and truly works as a great insulator.  However its hard to get glue in between everything (thats why I advise ensuring no crosstalk before this).  After that I wrapped the wire in aluminum tape.  I used a male DVI to female HDMI adapter and a short HDMI wire to connect to my computer.

The completed wire
Finalized with Important Wires Labeled
Above you can see that 3 wires have to be allowed to emerge from the DVI cable itself.  These are the wires connecting the 3 12V to the Yellow Molex (White Wire), wires connecting the 3 +1 Grounds to the Black Molex (Black Wire #1), Yellow Inverter cable on/off to resistor to the Hot Pink/Red wire interface (Green Wire).

Also the inverter cable can be seen next to it with a Yellow cable emerging from the Blue and Red Inverter Wires and going to the 24V up converter and a Black cable emerging from the Green and Black Inverter Wires and going to the 24V Ground up converter.

E) Optional iMac G4 wires (WiFi Antenna, LED Power Indicator, Microphone)

Soldered Cable
1.  WiFi antenna: There are a few extras wires in the base and from the neck that can be used in this mod.  In side the base you will see two antenna wires emerge from a hole in the base.  These wires go to an antenna that wraps around between the faraday cage and the white plastic of the dome.  The faraday cage is built to suppress electromagnetic signals, so it impedes Wifi.  I used a Broadcom PCI express wifi used in MacBooks for Lion compatibility.  This has antenna holes that connect to an antenna (You may need to sacrifice a third party antenna to get the connector).  I then soldered the inner wire and shield to the iMacs wire.
Secured with Electrical Tape
2.  The LED.  These are two small wires (red and green) that emerge from the neck with the microphone wires.  If you have some motherboard connectors you can solder these wires to them and then connect to the power LED on your motherboard.
Hooked up to Motherboard Power LED.
Also seen are the antenna hooked up to the Broadcom Wifi
Tip, Ring, Sleeve
3. Microphone.  The microphone has 3 wires a thick black, a thin black, and a red wire.  This has a TRS (Tip, Ring, Sleeve) arrangement.  For more details see my iSight Post.  Take a 3.5mm Audio Cable and cut it - three wires will be seen.  The colors may vary, but you need the Ring (Red in my wire) and Sleeve (non-covered in my wire).  Connect the Ring to Red wire of the iMac mic and the Shield to the Thin Black wire of the iMac mic.  The Thick Black wire of the iMac is not connected.  Nor is the tip (the white wire in mine) of the 3.5mm cable.  Also make sure the white wire does not touch anything.  You can hook the 3.5mm jack up to any mic source.  Since my onboard audio is not lion compatible, I plugged this into Turtle Beach's USB audio adapter's mic then into a USB port.
In the audio out port I plugged the 3.5mm audio extender as this will be wired to the back of the iMac (to the rear ports).  Speakers will plug in here.
Testing the LED and Microphone with
Alligator Wires
Turtle Bay USB Audio
F) The Computer/The Base

Now you can connect your power to any molex source and your DVI to any compatible video source,  Your internal designs may vary but this is what I used.

1.The Components:

Motherboard: Quanmax KEEX - 6100 Sandy Bridge ECX Motherboard
CPU: Core i5 Mobile 2520M
RAM: 1 x 4GB 1333 DDR SO-DIMM (Can support up to 8GB)
Power: 160-XT Pico Power Supply with 4 pin power plug and external Power Brick (+ up converter)
DVD: Lite-On 24X DVD Burner with Lightscribe support
Fan/Heatsink: Dynatron Socket G l2 Mobile Cooler
Compact Flash: (Optional - Mac OS will not natively recognize this in AHCI mode) - I installed
                          Windows 8 DP on this.  Transcend 32GB CF Card
Audio: Turtle Beach Amigo II USB Sound Card
PCI Express Wifi: Broadcom BCM94322MC PCI express Wifi
Extras: 16GB USB stick for Lion installation
            Griffin iFire Adapter for speakers with PCI express to AC adapter
            Sheets of Styrene
            iMac G4's DVD and HDD cradle
            Hard Plastic Spacers
            Computer Screws
            Rocker Switch
            Computer Power Momentary Switch
            Computer Pins and extra Wires
            2.5" SSD Rubber Case
            Hot Glue Gun
            Modeling Clay
            Gorilla Glue
            Double Sided Mounting Tape
            Aluminum and Electrical Tape
            Motherboard Pins to 2 USB ports x 2
            Cable Ties
            Bluetooth USB Dongle (Was an extra, not exactly sure of make)
            Wired Keyboard and Mouse
            Male DVI to Female HDMI adapter
            Short 1 foot HDMI cable
            (If your PSU does not have a 4pin power then you need a Molex to 4pin adapter, this one did)
            4pin PSU power female to male extender
            SATA cables x 2
            SATA power splitter (PSU had only one SATA)
            3.5mm Audio Jack Extender
            Ethernet Extender (I used an ethernet splitter and dremeled off one side).

Software: Purchased copy of Mac OS Lion, Tonymac's Unibeast, Realtek or Intel's Gigabit Ethernet Kext
Note: I installed Lion externally and I recommend doing this to ensure compatibility and to ensure everything works before placing everything inside.

2. Setup

Wire Management
You will notice that I opted against a case fan.  The fan actually presses into the board when using the native adapter (This should give you a sense of just home little room there is above the drive).  Initially I had a setup with a smaller 80mm (native is 92mm) fan sitting directly above the board.  I tried multiple setups with both an active and passive cpu fan (Cooljag makes a passive Socket G Heatsink) and the case fan blowing both in and out.  Although blowing in kept the overall board cooler, it only helped with the passive heatsink (active heatsink alone was better than this arrangement with passive heatsink).  Blowing out made only a marginal difference unless the fan was ramped way up (then it was very loud).  The best compromise I found was using smart fan settings in bios to ramp CPU fan up when temps exceed 65C on the CPU.  This allows the computer to be whisper quiet doing almost any every day task, while not allowing CPU temps to go too far over 70C under high load.  Note that this requires compromise, the motherboard is essentially in its own compartment with its fan placed directly under, only a few cms from the exhaust, the heat generating component of the PSU is external, and I did not go for a quad core mobile chip.

Alternative Design: I debated for a while if I should do this or to loose the internal optical drive and use a 92mm case fan as well (as a second internal fan vs heat pipes or small liquid cooler), with a more powerful cpu heatsink and cooler and the native psu.  This would allow me to place the board somewhat lower to fit the native psu and properly cool it.   Thus, I could use a more powerful mobile processor core i7 quad core.  In the end I decided I did not need bleeding edge power and I opted for a closer to original iMac G4 experience with quiet operation and onboard optical drive.  Though I am tempted to try this in a future build.

You may ask why I didn't use a male version of this DVI interface, the answer is that I couldn't find one.  This interface is so by far the best way to go, not only in terms of ease, but in terms of stability.  Almost all my mods where I solder the Black LCD cable to a DVI or HDMI result in some pixelation or distortion and I have heard the same from readers as well.  If a solder point changes resistance even a little, you will have image problems.  So I added an HDMI adapter and short HDMI cable.  I secured these to the top of the dome.  I used aluminum tape to position and hot glue to secure.  Using cable ties I made the wires as short as possible using the sides of the top of the dome (one of the only areas of free space).

Lay it out as its supposed to work
Turn it on with everything hooked up as it should be one last time.  (Nothing is more frustrating than having to disassemble everything to fix one small thing.  Note: There are two different ethernet ports with two different chipsets.  Use only one, (both have available kexts - choose which one you want and install that next).  I used the Intel Gigabit and then disabled the other LAN in the bios.  I hooked up the ethernet extender to this one.

I also modified the drive cradle, cutting off the pieces on top of the optical drive that were meant to cradle the HDD.

3. Installation

I used a hard rubber spacer and dremeled screw holes into 4 pieces.  I used a thick piece of styrene to use as a motherboard tray.  I personally like styrene as its firm, non-conductive, but is easy to cut.

Screw in first to determine placement

 The spacers were glued into the proper positions (screw holes) on a sheet of styrene that was slightly longer than the ECX motherboard itself.  This is important as you do not want the motherboard to lay flat, some ventilation must exist for the underside of the board (contains RAM and Compact Flash).  Then I screwed the motherboard onto its styrene tray via the spacers.

Fit testing

The image on the right is a fit test.  I used aluminum tape to secure the board and adhesive to make sure the optical drives cradle came into contact with the styrene.  Notice that the board is right of center.  This is done to allow the bulky cable plugs, USB and HDMI to fit.  Wires also come down from both sides depending on where I need it to go.

When I was secure in my position, I glued the styrene onto of the optical cradle on all put the leading edge.  As you can see there is a metal tray that I left in place.  This leading edge allows me to slide this edge of the styrene with motherboard on top of this tray.  The other sides are glued to the drive cradle.  Which can then be screwed into its native holes.  Thus, the motherboard is double supported.

Make sure all cables are to the sides and that no wiring goes over or impedes the fan on the motherboard in any way.

With the DVD installed you can see how little room is left.  As a matter of face to two areas on each side of the DVD are all we have left for our power source and up converter.

The placed the PICO PSU to one side and the up converter on the other side.  To give myself more room I did cut down the "wings" of the up converter with a dremel, though this is likely not necessary.

Below the drive there is just enough room for the 2.5" drive to squeeze.  I put this in a rubber internal 2.5" HDD case and with velcro secured it to the bottom of the drive right above the access panel in the bottom of the iMac.  This may not be the most elegant solution, but it works great.  As most of the boards over specs I'm unlikely to change, the SDD is something I could see myself swapping out.  So unscrew the bottom panel as if changing the RAM or adding an airport card in the original iMac G4. Pull off the SSD in its case enjoy the satisfying tear of velcro, swap it out and put the new one back and you are done.

4.  Power Button and Ports

One way to do the power button is to secure your momentary switch right behind the original power button.  This seemed to work great , but I unfortunately pushed in too far one time and dislodged the power button.  So I swapped it out with a small threaded black power button for now.  I am awaiting delivery of a smaller silver power button of the same size.  Although the native switch is more elegant, I do not want to worry about how hard I press the button.  The threaded power switches are bolted in and therefore more stable.

How far you want to go with ports is up to you.  The easiest solution is to let the wires poke out the back as I did initially.  Another way that I did it initially was to use the ports I created as part of my Core 2 Duo ECX mod

Using modeling clay to secure the USB and Ethernet ports.  Some dremel modification was needed.

 I removed the unnecessary wires and replaced them with the current ones, this time using hot glue.  However, I was having some instability with the ports.  Occasionally pushing the panel in.

Ultimately, I decided to secure the extenders from the inside.  So that what ever I put over them would just be a "covering".

 I designed white styrene "caps" for these ports.  But, I am holding off for now as I have actually invested in Makerbot's replicator (3D printer).  As a modder, I can't tell you how many times I wish I had "a little piece shaped like X" - hopefully "with a learning curve" I'll be able to figure this out.  Once it comes my first project with it will be port covers.

Also, I had initially intended to internalize (even took it apart) my ifire, however I felt is was too much of a power drain.  So, the ifire is external.  As I don't have a firewire port, I used a firewire to AC adapter.  I made my own, but apple did sell one, and they are easily obtainable.  You do not have to use the apple pro speakers, I just have always liked the way they looked.  If you don't have an ifire and are interested in this speakers please see my extensive post on my experience and advice with these speakers called Proprietarily Ridiculous - The Apple Pro Speakers.

Completed Mod
So thats the 20".  As you can see this is not the only way to do this.  But as with any mod dealing with a tight space you have to make compromises.  I honestly believe this is the best balance I can achieve at this time.  As technology keeps improving and things continue to shrink, this will likely change.

I have been using this extensively over the past several weeks and I am thrilled.  Its fast and powerful and I have yet to hear the fan have to crank into high gear.  As I mentioned I did add a Windows 8 DP dual boot, which has also been fun to play around with.

This mod is a culmination of years of hard work for me.  This is what I had hopped to build when I started but quickly found that it was impossible.  With every successive attempt I felt I came closer and closer and have now completed what (as little as 6 months) did not think was possible.  I am also happy that I am able to share it with others who also love the design of the iMac G4.  One thing I did not like about my other 20" mods is that I didn't feel they could be easily reproduced, I can confidently say that using the DVI connector I discussed this mod can be done by someone with minimal modding experience.  I appreciate all the feedback and as always am happy to answer any questions.

I would also like to give my appreciation to other modders pgee, JeanLun, and bluegray without whom I would have been stuck at various points along the way.

Thanks for reading!!


  1. If I understand right, so you are trying to build a Hackintosh inside a iMac G4! That's fantastic! I have a working iMac G4 20 and I am always thinking to get it some boost. Wish you luck.

  2. I am looking for guidance/counsel from an experienced one.

    I have a 17" iMac G4 (1.25GHz) with a bad display.

    I also have a 20" iMac LCD with no back housing.

    How do I connect the 20" display to the 17" inverter?

  3. William, thank you very much....things are coming along nicely, stay tuned.

    Reinheimer - I'm happy to help. Unfortunately, there is no way to do it. There are 6 ccfl lamps on the 20" and only 2 on the 17". Even if you could "distribute" the voltage between the lamps the display would not be bright enough to be useful. A 20" inverter and LCD housing can be found on eBay for probably $20 each if you wanted to "complete" you LCD.

  4. Hi Jberg, I've read your blog from top to bottom. Thank you for sharing your knowledge with everyone! I recently inherited a working 15" G4. You hinted that it's nearly sacrilege to rip up a working G4, but I don't know what other use I would have for an 800MHz machine besides using it as a high-wattage photo viewer or very slow web surfer. That said, I'm probably going to rip it apart anyway and put an itx board inside. I won't bother with an optical drive so I'll have room for a decently sized fan. Won't start the project until after January, so I have time to consider all options. Just wanted to say thanks!

  5. Wow, I also have a 20" iMac which isn´t working very well. I can´t wait to see the rest of your step-by-step guide.
    Thanks a lot JBerg!!

  6. Envador - Thank you for the kind words and I wanted to apologize if I sounded "preachy". It is not up to anyone else what someone chooses to do with their own property. My own basement is littered with the "carcases" of used electronics and failed projects. Based on people who contact me I'd estimate that less than 50% of people who start this successfully finish for whatever reason. I just didn't want to encourage people to buy working machines from eBay - tear them apart and then dump them - when there may be people who could have used the original machine. I have no problem with you modding your iMac however you see fit and I am available to provide any help should you need. JB

  7. JGml - sorry for the delay it's actually more software related than hardware which is set to go. I will be completing this shortly.

  8. Hi JBerg,
    Thanks for the write-up, which makes me pull the trigger on a used 20inch iMac G4 finally.

    Just tore it down. Planning for the mod.

    1) The Bulky Optical Drive and 3.5 inch HDD will be eliminated so I think there will be more room for standard parts.
    2) Would rather go the Mini ITX way, your ECX mod is impressive but I prefer the choices on CPU, heatsink and ECX board+Mobile CPU is pricy to me.
    3) I am not familiar with LCD part. So except the genuineness, any other goods with factory LCD panel? Or it is just the inverter which is hard to find for aftermarket panel?
    4) PSU part, how much possibility is it to use the native power supply? (20 inch iMac G4 has a 190 watt PSU, should be enough for everything, I am not sure but wouldn't the 16pin connector ready for 12v, 5v 3.3v, and maybe 24v?)


  9. Edwin, I'm glad to hear it, and I'll do my best to answer your questions. 1) you are correct, if you use a mini itx you can not fit an optical drive. Lots of options for hard drives exist today 2.5", 1.8" or even other types of flash memmory ex. Pci-e, compact flash. 2) don't want to sound like an ECX pusher but there are different and cheaper alternatives. Remember the KEEX - 6100 is the "top of the line" in this category, but core 2 duo, solo, atom, amd options do exist. If you use a mini itx, consider a liquid cooling option whereby you can carry the heat from the processor to the exhaust at the top of the dome. A mini itx does fit (albeit at an awkward angle and some ports may be blocked), but airflow is non existant in the metal faraday cage. 3) I am not sure exactly what you are asking. The panel is really a whole monitor with the LCD controller inside the LCD itself and the special very thin inverter. 4) yes the native power supply has all those voltages. However, It did not fit in my design and I have experimented with 2 power supplies. In both cases they were either broken or not "jumped" in a standard fashion. But, I'm sure it's possible

  10. hello, quick question, i am trying to reuse my G5 isight 17" LCD, but i have question regarding the invertor, the invertor has 4 pins out, do you know which one is what? (as my G5 mobo is long dead,,,,)

    similar to you, i use itx board from BCM

    and with C2Q 9100 and GF520GT through PCI-e 1X for CUDA,

    i am attempting to get it working though either DVI(geforce) or Intel HD4000 (LDVS), the board does have invertor control but i dont know if the pin out match, and if i use dvi, i will need to be able to manual control the invertor...

    my email=allenpan (at) hotmail (dot) con

  11. this inverter is what i have:

  12. Just a note to all people regarding the post Envador made:
    I am currently typing this message flawlessly on an iMac G4 with only upgraded ram (1GB). If you are unsure about going all the way with your mod then I suggest tanking a look at MintPPC (a version of linux based off of Debian to bring life back to older PPC systems. It also works on the xbox 360!). It simply runs flawless and has allowed me to use the imac g4 as a small ftp, ssh, and web server. I also use it as a decently fast (comparable to smart phones, due to very similar specs to iPhone 4 and other pre-dual core smart phones) web browsing/social machine. The only tricky part was to get the drivers working for the original speakers. Yet, eventually, it all worked out. Just an idea for some of you, I'm not trying to hold back modders because I too plan to eventually mod this thing. But if you also have an old mac laptop (with a PPC processor in it) then this is also a solution for you.

    Just a note that there is no flash support with mintPPC, and HTML5 flash runs just as choppy as OSX would on the G4.

  13. Hi JBerg! When will you finally finish your iMac G4 "Genuine" Mod?
    I can´t wait to mod my own one!!


  14. JGml - the mod has been done for some time and now the guide is done. Enjoy!

  15. Hi JBerg, your new blog looks really great! I like it!

    I´m trying to mod my own iMac G5 with your 20" Guide. Seems good :)
    But theres one thing which I don´t get.

    At Point II./D)/7. you recommend to connect the yellow wire form the converter to the hot pink wire. I don´t understand which wires you mean. The hot pink wire is still connected with the white "extra" wire, isn´t it? And which yellow wire do you mean? The one which comes out of the grey lcd cable and goes to 12V?
    And to which wire have you connected the new green one?

    So you see I don´t get step 7...

    Hope you can help! Cheers!

  16. JGml, thank you very much. Sorry to confuse you. The yellow wire I am talking about is the from the Inverter. Right now you should have 5 of the wires that come from the inverter hooked up. The Green/Black hook up to the ground of the upconverter and the Red/Blue hook up to the 24V of the upconverter. In addition, the Yellow Inverter wire hooks up to a 6.8Kohm resistor and then to 5V on the Molex. Think of this wire as an on/off, if it gets power, the backlights will be on. The annoying thing about this is that the display can be off, but the backlights will stay on.

    A "trick" to eliminating this is to get the 5V from the DVI source. This is DVI Pin 14, where 5V is given by the source/computer. I connected an orange wire to pin 14 and then split it. One side connected to a white wire (unaltered - no resistor), then to the hot pink/red wire. The other split/side went through a 1Kohm resistor to a yellow "extra - not the wire inverter yellow" wire then to DVI #16 (The hot plug).

    We need another 5V from Pin 14, for this you want to split that 5V again, but it must be unaltered (not through the 1Kohm resistor). You could take it directly from pin #14 (crowded), from the orange to white wire interface, or from the white wire to red/hot pink interface. As this is an optional step, I felt that this is the easiest place to take it from. So you leave the white "extra" wire and hot pink together but you add another wire that splits here. I used a green wire and wrapped around this inferface. Then connected that green wire to the 6.8K resistor and then connected the resistor to the yellow wire in the inverter cable. So the 5V essentially comes from DVI pin 14 and no longer from the molex.

    So when the DVI does not send an image (ie sleep) the backlights will turn off.

  17. Hi JBerg, thanks for all the details you have post here. I just have one question. Does the TMDS to DVI work with the output from my laptop which is actually a display port or HDMI to DVI ?

    1. Display Port should work, but it's a different standard, so I can not say or sure. HDMI using a simple adapter will 100% work. hDMI uses TMDS as well, this is the setup I currently use for both my 20" mods. One uses HDMI to a Mac mini, the other HDMI to the ECX board.

  18. Thanks JBerg! Now i finished theTMDS to DVI Mod but there is still a big problem. I plugged in the pico psu but there is no power coming out of the cpu. i tested the power which is coming out of the big power brick and there a 12V. So it seems that the pico psu is turned off if that is possible. Do I need the rocker switch you described in your guide the turn the psu on? If yes which pins exactly are the jumper pins?

    I never done a mod before and I have no electrical skills so I really have no idea how to get power out of the pcu...
    But I love the iMac and hope that I get it fixed :)

    Tank you so far!! Cheers

  19. JGml, yes any atx PSU thats does not have its connector plugged into a mobo, needs to be "jumped" to output power. This can be done by grounding the green pin. As most pico psu's don't have colored wires, you have to count. This will vary if you count the wrong way between different power supplies (some are 20 pin - with 10 on each side, some are 24 pin - with 12 on each side. The best thing to do is count from right to left with the clip FACING you. The green pin will be the 4th pin from the right. You not need a switch, but you have to connect that pin to a ground. That pin is surrounded by grounds. The two pins on each side are grounds. So take a wire or a paper clip, shove one end into the "green pin" and the other into the pin to the right or left of that pin, doesn't matter. See my pictures at the very top of the article. The red PSU is a 20 pin, the green wire connects the 4th pin from the right to the 3rd pin from the right (with the clip facing you). The yellow PSU is a 24 pin, the black wire connects to the 4th pin from the right (then goes to a switch) and the yellow wire that comes back goes to the 3rd pin from the right. Again the clip is facing you.

  20. Hey JBerg! Thank you again. Tried to jump the PSU but still no Output. But I tested the display without the PSU und it works!!
    It´s great! I´m so happy :)
    I´m sure that I will solve the PSU-problem. Maybe it´s defect... I will tell you if I get the iMac to run! And hopefully send you some nice pics :)
    So a thousand thanks again, your work and help was fantastic!!

    Cheers, JGml

  21. JGml, I'm honestly thrilled to hear about your success and it's why I made the blog in the first place. Good luck with the PSU and def send pics whn it's completed.

  22. Hey JBerg,

    I am interested in the same kind of build and was looking around for some boards untill I stumbled upon the following board: Intel DH61AG ( I was wondering about your opinion about this board and how it would fit in this kind of build.

    The boards has some special features like a slim profile, built in power source and a component for controlling display's, I quote from the review:

    "Further across the board we have the LVDS/eDP connector designed for uSFF HTPC and AIO systems. Complementing this connector is a series of jumpers that allow display voltage selection, backlight inverter voltage control and display brightness control."

    I apologize in advance if it's a dumb question, I was just wondering about your opinion on this board.

    1. Found this link on an intel site, check the components numbered 23, 22, 20 and 19. It seems that the inverter component is probably not compatible since it only supports 12v and 19v and if I remember correctly you stated that 24v was needed to power the inverter. Too bad...

    2. This link:

    3. I don't really know anything about this board. I personally do not think the mini itx form factor really works in this mod. It barely fits (often several ports are no accessible. It takes up the entire bottom of the dome, meaning anything you put above it will block the minimal air flow the dome allows and powering them can be a problem. But, I have never used this board or any other low profile board, but based on the length/width of the mini itx form factor, its likely not ideal.

      Most embedded boards will have the ability to directly power an inverter and support LVDS signaling. However, most of these tend to be for small LCDs, so the voltages for both powering the LCD and backlights are usually inadequate for larger (i.e. 20" LCDs). The backlight here does take 24V as you pointed out, but the larger problem is that the iMac G4's LCD uses TMDS signaling and not LVDS. If you wanted to change to an LVDS LCD, you'd have to rewire the neck. TMDS actually has several advantages and I would not recommend changing. Most motherboards come with a TMDS out, its the DVI/HDMI signal, all you have to do is add the power and place the pins in the right orientation.

    4. Hey JBerg,

      Thankyou for your reply, I will drop the boards and follow your guidelines.

  23. Great article. What would I need to do to use a 17" g4 with a logic board from a 20"?

    1. I assume you are talking about using a 17" LCD with a 17" neck with a 20" logic board. To be honest I'm not sure I would attempt this, there would be a big risk of damaging the logic board, the lcd or both. The 1/1.25Ghz 17" matches up better with the 1.25ghz 20". Which power source would you be using? You'd have to make sure the power source could power the 20" motherboard without problems.

      The biggest issue is power. You'd have to downconvert the power to the LCD panel from 12V to 5 or 3.3V. Then you'd have to change the power to the inverter from 24V to 12V. There are also several inconsistencies that may come up. Certain 17" models have less metal convection contacts for cooling. All in all I think you'd be better off getting a new matching 17" LCD or getting a 20" neck/lcd, but if you are dead set on it, start with downconverters for the lcd/backlights and see what happens (but its risky).

    2. Hmm. doesn't sound promising. I figured i'd just have to move a few wires around. I have a 17" 1.25Ghz machine with a fried processor. I got a logic board off ebay but it is for a 20" 1.25Ghz machine. J14 on the logic board has a couple extra pins. I've been searching for a pinout of the j14 connector for both the 20 and 17" logic boards, but have not been successful. I'm not too terribly interested in lots of work--i just need a machine to run Lego NXT software for my First Lego League team to use. (i'm 36 bucks invested so far...) Before it died, the 17 was rock-solid but slow. My intel mac-mini is fast but unstable. If it isn't too hard, i'd love to just make this work. It sounds like its not so easy though...

      I'm not too worried about frying anything as a dead machine is a dead machine--(or MOSTLY dead, as Miracle Max would say)

      I do appreciate your reply--if there is an easy fix, i'd love to hear it.. otherwise, the salad-bowl will go back into the closet...

  24. Wait... if I put the display from the 20" apple cinema display in my 20" g4, I wouldn't have to do the complicated wiring of the tmds to dvi conversion, right? It already has a dvi connection, I would just run the wires down the neck and put the power brick in the base and then my g4 would be an monitor.

  25. Nvm! I see now you have already answered a similar question, the inverter and LCD controller will prevent it from fitting, so some complex wiring is unavoidable

    1. Yes, they wont fit. But, with the addition of an extra wire, you can use the native iMac G4 inverter with the Apple Cinema Display. Then you can put the controller in the base. This does mean lengthening and altering the wires, but this is a very stable setup and its one that I am using almost daily. Please see my 20" ACD controller mod in May of 2011. These posts may help: glass.html

  26. Hi! I would like to do this but my knowledge in electronic and in english are so poor...
    To make simple, I found an Acer 20'' lcd monitor with his own alimentation and VGA out. The problem is that the Acer inverter card can't be placed behind de screen. Not enough space. Do you think I can use the Apple inverter card with the Acer display ?
    Cables arriving to the Acer invert are the following :
    1. +5V
    2. +5V
    3. GND
    4. +3.3
    5. +3.3
    6. GND
    7. ON/OFF

    Thank you for your help. Wy do not bold a forum ?

    1. Unfortunately no, the voltages of the apple cinema display are quite different.

  27. What an Awesome Site!!! I have recently been given a 17" G4 and 2 15" G4 and my 14 year old is all about building a computer with his old man. It is a right of passage the older one went through last year making a windows gaming machine with water cooling. The younger son has Fallen in LOVE with the G4. This will be a project over the vacation break. I have NEVER done this before and am reading up on your site. Looking for a Kit of parts that we can use to do the conversion Do you have a current list with the best processor/combo for doing this? Also any thoughts on replacing the 17" with a 20" Touch screen? Costs? Thanks in advance.

    1. Hello KCP, I appreciate the compliment and am actually thrilled at the prospect that my blog would be the focus of a father/child project together. Repairing and replacing components of machines like 386s and commodore 64s is a lasting memory I have with my own father and can't wait til my kids are old enough (a hopefully have interest).

      So, currently Quanmax' KEEX 6100 with a mobile Core i5 (2520M) - Sandy Bridge - is my most advanced absolutely completed build. That said, I am nearly done with two Ivy Bridge Boards. Aaeon's EPI-QM77 with a mobile Core i7 (3610QM) and Intel's NUC QS-77 with an embedded Core i3 processor.

      It really comes down to Cost, If you want an all-in-one, Want a hackintosh, and how powerful you need this to be. Using the guide and the DVI connector, you can connect this to an external computer source. Making an all in one is obviously more involved, but also could be more fun. The small form factor boards tend to be specialty items and can be quite expensive. The EPIC board and processor can run $600 - $1000, depending on which processor you choose. On the other end Atom/Fusion/VIA Pico boards can be $100 - $200, but will not be powerful or capable of running OS X 10.8. ARM boards such as the raspberry Pi can be even less expensive and can run android or other ARM Linux distros. Just because they are cheap doesn't mean they would be any less fun to tinker with and there is an excellent helpful community of people working in these boards. If a capable OS X machine is the goal, I'd probably recommend the Intel NUC (though I'd wait until I have finished my mod with this board to confirm it). It has a good balance between cost/performance, though at $300 it's still overpriced in general, but not bad for a hobby board. It includes the processor, though this means you won't be able to seat the processor together as part of the project, the RAM, mSATA drive, and wireless card must be chosen and installed. Plus, as this is intel supported an consumer aimed, it's available from Newegg and Amazon and will hopefully be easily upgraded in the future.

      In terms on monitor upgrades, the necks of the various sizes are different, so that a 17" neck will not support the weight of a 20" monitor. I have done a few touch screen G4 mods

      Though do have to warn you that this will add a layer of complexity and cost. I have not been happy with the resistive screens and have been investigating other technologies. The limiting factor is that the 20" and 17" are 16:10, a ratio no longer commonly available. I have tracked down a 20" 16:10 capacitive screen by 3M, but it is expensive, thick, and heavy. I am hopeful that touch films will soon be available, making this much easier.

      I hope this has been helpful and am available for any questions or assistance.

  28. Would you consider building an imac 20", as illustrated above, and selling them?

    1. Unfortunately no. These are far too time consuming and the parts involved are old and sometimes quite expensive. The price would be far too high to make it worth it and even then you're still talking about parts that are a decade old and could fail. I would not want to offer tech support, so it really would be a benifit to understand the construction as to troubleshoot problems in the future.

  29. Thank you so much for this guide!! I am working on converting my 20inch into a monitor using the native PSU. I just finished, and am needing some help troubleshooting. I am only getting a black screen. I checked, and the PSU is working and supplying the 12 and 24 volts. The hot plug detect is also working, as the back light turns on when I plug it in. I do believe everything is hooked up properly, so what is the chance that the monitor is broken? (i bought on ebay with no harddrive,so I have not seen if the screen works) Also, I am testing it via a DVI-D to hdmi cord, is it possible that it is not compatible? Is there any key connection I should check? Also, I only used one yellow wire coming from the PSU to provide the +12 volts, is only one needed?

    I apologize for all of the questions, I just dont want to end up with a decorative brick. I was able to follow the directions but I dont really have a solid enough understanding to troubleshoot well.

  30. It's my pleasure. Unfortunately, the chances of finding a defective LCD on ebay are fairly high. I have the benifit of having spare parts that I know work which allows me to test components such as this. The DVI to HDMI should not matter, that said once I had a defective DVI to HDMI adapter that caused me to nearly tear apart my setup before I figured it out. So, I would try different cables before junking the LCD. With a digital signal it doesn't take much to get nothing. The hot pink VEDID is essentially the on switch, so pay attention to that one in particular. Using one yellow wire doesn't matter as they all come from the same place. Also, use a light and look closely at the LCD to make sure there is no image and its not just the backlight turning off. The one thing you can not do is share resistors.

    It could just be pins shorting out forging to close. With the PSU and computer on, press on the pins of the DVI connector ans look at the LCD, if an image appears for a moment you know you have a short. Failing this, I'd verify all connections with a voltmeter on a continuity setting. But it certainly could be a defective lcd

  31. Hi, Thank you for posting the guide! I'm trying to make my 20'' a external monitor using native PSU from the method u use from above, but i have a few questions
    1. Do i have to connect all the require cable to the same ground or any ground that exist on the PSU?
    2. How much Watt of the 6.8k ohm are you using?
    3. the PSU is "always on" means once its done, i can just plug the c5 and it will comes on?
    4. should i connect the required LCD cables to the 12V out or Molex 12V in?
    5. while i try to use the PSU cables, should i just cut free with the original plug to the logicboard and free the molex connected to it as well?

    thank you very much

    1. Hello hello Kin, I'll try to answer them one at a time. 1) Any ground on the PSU will do, they actually all join together anyway. 2) I believe they are 1/2 watt. 3) The PSU will supply 12V out as soon as you plug it in. 4) I am somewhat confused by this question. I assume you are talking about the molex on the original PSU. That is essentially a dead end, it's cables actually come from the G4 motherboard. You need to supply 12V from a live 12V wire coming from the PSU. 5) This will help with answering #4 as well. Yes, that's what I did, I cut and stripped them and discarded the molex (though you can reuse it).

    2. It works! Thank you very much
      but the screen shows some random green dots while playing a video, is it because of the cable connections or the resistors?

    3. Usually this is either crosstalk between wires or more commonly a ground loop. Some other electrical signal is not going to its proper ground and is instead dancing around the DVI pins. Try connecting ground wires to an independent psu ground one by one

  32. I was wondering if I could use this then install mountain lion instead. Will that work? I want to get more power on my iMac G4 and was wondering if I use this board would it be good for games like Portal, Portal 2, TF2, Source games like that. Would there be any heating problems? Not being able to run it? Thanks in advance.

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  34. Hi! I was in the progress of building my own "media display" with Raspberry Pi and display + touchscreen, but then I found this non-working 20" iMac G4. I'm now planning on just putting the Pi in the G4 and use its display (seemed to be working as it went white when I powered up the G4). I had already bought a 12V 8A power brick and 12V-5V step-down converter to power everything; USB hub (5V) - which will power the Pi as well (USB powered), LCD logic board (12V), touch screen (USB powered).
    But then I read the G4's display needs 24V to power up. So now I'm trying to decide whether to use the original PSU to power everything or buy a 12-24 step-up converter. Could you give me some advise? Could using the orignal PSU be overkill?

    It might be worth noting I haven't used any Molex cables (altough I possibly should have).

    Also, some images seem to be missing on the site? Other than that I love your guides!

    1. The lcd model number is the key. You can find a convertor board on ebay for it for about 35.00. This will solve the issue of the 24volts.

  35. hello, i just wanted to say thanks... this tutorial is awesome.. took me about 6 ,onths to finally get the resitors, (i know im slow) but just got my g4 display running with my pc... absolutly beutiful... the display has no right being so nice for how old these snowballs are

  36. hello, i just wanted to say thanks... this tutorial is awesome.. took me about 6 ,onths to finally get the resitors, (i know im slow) but just got my g4 display running with my pc... absolutly beutiful... the display has no right being so nice for how old these snowballs are

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  38. I got the upper half of a 20" g4 iMac from my brother: the lower half is yet to be found in a garage, I'll look for it if the display works.
    I made the connections to an HDMI male plug, very confortable to work with since it has numbered screw terminals for the pins.
    Now my questions: I didn't understand a thing in the power compartment of this guide. Where are my + and -? Why does the table state 'connect to 12v' when we need a step up converter to 24v? Is there a way I can power the LCD from one or two variable PSUs just to check if it works before I buy anything? Have I become stupid all of a sudden, or have I always overestimated myself?

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  41. Hi, is there a special name for the display wire from the motherboard to the display? And is there a way of connecting the video cable via HDMI without soldering?

    With kind regards, Janneke.

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