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.
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.
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.
|Plastic and Shielding Peeled Back|
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
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
|With Resistor Added|
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)
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|
|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.
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
SSD: OCZ 64GB SATA II 2.5"SSD
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 Power Momentary Switch
Computer Pins and extra Wires
2.5" SSD Rubber Case
Hot Glue Gun
Double Sided Mounting Tape
Aluminum and Electrical Tape
Motherboard Pins to 2 USB ports x 2
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.
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.
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.
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
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!!