Apple Cinema Display / iMac Mod Wiring the Neck Update

As I mentioned previously there are really two ways of getting the cinema display signal through the neck.  The first method was to remove the pins from the connectors when possible, remove all existing wires from the 20" neck and replace them with the cinema display cables.  This method has the advantage of minimal soldering (especially of the very small cables), but getting the wires through is tedious.  Although the wires are similar the shielding is thicker on the cinema display cables.

The second method is to use the existing wires in the iMac neck and solder them to the Cinema Display Connectors at each end.  (With one notable exception).  To start I removed all the protective tubbing from the cinema display cable.  The cable is composed of 4 separate wires.

1) The Power Cable - 3 wires - including 24V
2) The DVI cable  -  This cable actually splits into two parts on the monitor side of the cable
     A) TMDS Signal Wires - The equivalent of the black cable of the iMac - 4 triplet wires = 12 total
     B) TMDS Power/Data/Clock - The equivalent of the gray cable.  This contains the clock, data, hot plug, EDID, and ground.  There are less cables than the grey cable because the power (VCC and ground cables) come off from the lcd controller.
3) Firewire - I discarded
4) USB - 4 cables

The iMac has 4 cables as well
1)Microphone/LED
2)Inverter Cable
3)TMDS - Black
4)TMDS - Gray

 As I showed in my previous post, I didn't believe any existing wire was similar in gauge to the power cable, so I did have to open the neck.  I removed the microphone/LED and replaced it with the similarly sized Cinema Display Power Cord.  I then spliced the DVI cable to the existing iMacs Black and Gray cables.  As there are 4 extra wires in the iMacs grey cable I used those for the USB.  So the inverter cable is unused.  So if you need the room it can be discarded, but I am hoping to use those cables for the touch screen.  Remember to put the DVI end in before soldering the connector can not fit through the hole in the top of the base.

 In essence I simply cut the Apple Cinema Display in half and spliced the iMac Cables in the neck between them.  With the exception of the USB cable, I used the iMac cables that were meant to carry that very signal.  Meaning I spliced the Clock to the clock, EDID to EDID etc.  The most important thing is to write down which wire you spliced to so you can correctly match the wires back up on the other end.  Knowing the function of the wires is useful, however, for troubleshooting purposes.  The guide I used is shown below.

   Having done both methods, I would recommend using the splicing method.  The reason for this is that although there is more soldering, you end up with a surplus of wires.  Thus, if you want to add firewire capability, a touch screen etc.  you have that option.  Also, it is easy to damage the neck when trying to force the extra wires through.  Testing it out:

:

20" Apple Cinema Display/iMac G4 Mod to Date

 This is without the front bezel of the iMac G4 on top of the apple cinema display.  The bottom is also not on as I am now working with the components in the base.

The touch screen does not fit inside the monitor housing.  Because, I want to make the touch screen removable, I originally had the controller inside the casing and sacrificed a USB port internally.  However, the touchscreen could not be removed without taking the entire monitor apart.  So instead I bonded it to the iMac's Front bezel to make sort of a USB Touch Screen Overlay.

With the touch screen and bezel in place













Unfortunately, the VESA mount method does not work with the cinema display.  Although the weight is identical to the native iMacG4's monitor, the VESA mount displaces the monitor forward about an inch.  This puts too much pressure on the neck and the monitor will not stay up.  By putting the neck directly into the back this problem is eliminated and it moves exactly like the native monitor.  To finish it off I sealed the holes using gray styrene

 This shows the temporary housing for the touch controller.  The white strip is a protector for from the touch screen.  I'm still not sure how to handle the touch controller.  I do want to make it easily removable (It does add a lot of glare to the monitor and I'm not 100% I am going to keep it for this mod).

I came very close to painting the back white.  I do think doing that would make it nearly indistinguishable from the native iMac G4s monitor.  But, for now I held off.

Obviously, this isn't the native iMac, but it is pretty damn close.  Unlike the TMDS to DVI 17" mod, I don't have to deal with screen corruption during sleep.  To use the original 20" inverter I would have needed a 24v, 12v, and 3.3v power source - for the monitor alone.  The backlights would have been turned on independently - which is somewhat inconvenient.  I still do need the power brick, however, which I may not be able to fit in the base.

I am very curious to hear opinions and suggestions regarding how to improve this mod.  When I am finished I can post a parts list, step by step guide if anyone is interested.

Next step: I am going to complete the alternate neck wiring method I described in my previous post.  I may paint the housing white.  I also need to decide how I'm going to handle the touch controller, make it look clean, but keep it very easy to remove.

In terms of the base, while the ECX board can boot off the compact flash, its onboard graphics is unable to drive the 20" monitor.  As a result, I will need a dedicated graphics card.  Because it has only a PCI x 4 slot, I have decided on the Zotac Ion PCI x1 card.  With a pci riser it should still fit, but its starting to get very crowded.

Wiring the Neck

5pin connector

Cinema Display TMDS

 To wire the neck there are really two choices. 

OPTION 1: You can replace all the native iMac wires with the apple cinema display wires.  The advantage of this is that you don't have to solder the very small wires.  I simply removed the tmds wires (using a safety pin) from the JAE connector and 5 pin connector put them through then reconnected on the other end.  Only on the 3 wire power cord and the 4 wire USB cable did I have to cut off the connector and resolder at the other end.  However, getting the wires through is a huge pain.

TIP: Put the wires through the base first because the DVI connector is too big to fit through the opening.  so once you solder its too late.

To open the neck I again used a taped together mini screwdriver set.  It is not difficult once you get the first turn done.

So open and replace the wires.  (I'm using a neck from a previous mod - so the wires pictured may be unfamiliar).

Getting the wires through can be very difficult.  My advice would be to just bite the bullet and take the spring off its moorings put the wires through and then get it back on once completed.  Sometimes using a small wire to put through then wrapping around the actual cable and pulling through can help.

OPTION 2: Hybridize with the native iMac wires in the neck.  There are the 4 triplet pairs which carry the TMDS image (This is the top of the TMDS connector pictured at the top of this page).  The wires at the bottom of the image actually come from the control board so do not need to go through the neck.  There is an additional 5 pin connector (pictured above) that comes from the DVI and goes to the control board.  Although I haven't verified I suspect these are the hot plug, vedid, clock and data edid, and ground wires.  Although these are a slightly larger gauge than the wires in the iMac gray wire - they should carry the signal fine.  (you will need only 5 of these wires).  The iMac's inverter cable should work fine to carry the USB signal.  Unfortunately the power cable (and its 3 wires) carries 24V and none of the existing wires are adequate.  However, you do not need the microphone/lcd light cable, you can remove it.  This leaves room for the Cinema Display's power cable.  Like the above option, you do have to cut and resolder the cable.  The only one I'm not 100% sure about is the smaller gauge iMac gray wire carrying the wires from the 5 pin connector.  If that doesn't work, I plan on using the inverter cable to carry that signal and will replace the gray wire with the USB cable from the apple cinema display.  Below is the resealed neck with the Cinema Displays cable in place.  Of note, be careful how much cabling you leave on the monitor side of the neck.  Its still a tight fit in the monitor housing.


Getting through the one cable in place of another is not difficult.  However, the challenge is that it will require soldering on both ends.  So the tiny TMDS signaling cables 4 x 3 = 12 will need to be soldered on both ends = 24.  The five 5pin connector x 2 = 10.  The USB x 2 =8.  Its certainly doable and I will post when this method is verified.

My 20" Solution

Looking at the 20" iMac Power Supply there is a 24V line, so I figured the inverter probably had a 12V and 24V (two seperate grounds), a dimmer (which works backwards as previously noted), and an on/off.  Unfortunately, I seem to have guessed the wrong wire and burned out my 20" inverter.  I had purchased a broken Apple Cinema Display (Cracked Screen), figuring the inverter still worked, so far has been the only other inverter to fit within the iMac's case.  However, this inverter DOES require a 24V line.  I wondered if its possible to fit the inverter as well as the LCD controller in the back on the iMac since they are the same depth.  Doing this would require modification of the iMac's back casing.  I tried dremeling off those X's - it fits, but it is tight.  The cinema display had several advantages over the iMacs native display.  It uses TMDS signaling via the DVI cable, but supplies its own power and has its own controller.  This solvesthe need to supply different voltages and resolves the screen corruption issue.  It has USB slots as well as an independent power/brightness button.  It also sends its TMDS and power signals through a few relatively small, shielded cables that are similar in size to the native iMac's.  As I began thinking of more and more ways to alter the iMac's casing (cutting areas for usb ports, power and brightness control, fitting in the LCD contoller/inverter and wires), I began wondering if it may be easier to go the other way - to alter the apple cinema display to fit on the iMac G4s arm.

The monitors are remarkably similar, they are the same depth and size.  They are also EXACTLY the same weight (without the stand).  Although the cinema display has more things in it, its aluminum casing is lighter than the iMacs metal and plastic.  The only problem is that the hole in the Cinema Display is too low.  The monitor is designed to be vesa compliant so the back can support its weight.  A metal piece is glued down, but easily removed.  As you can see it is designed to hold a long thin bracket, not a ciircular object, so I had to find another piece to secure the monitor.

By removing the pastic around the metal housing of the iMacs monitor enclosure, I was able to cut a makeshift bracket of similar size to the cinema.  The depth was also the same.  This will give me the circular pattern I need to secure the iMac neck to the cinema display's housing.

I placed the cinema display housing into the iMacs in order to line them up and determine where the "circle opening" needed to be. After this I drew and was able cut out the opening with a dremel and tin snips.  I then placed on my "bracket and closed the monitor to ensure that it fits.  The final step was to glue down the bracket when I was sure everything was centered properly.

Inverter Frustration

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

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



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


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

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

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

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

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

17" DVI Pinout Confirmed

UPDATE: Please note that there are TWO DIFFERENT 17" necks.  This one works only for the 1 or 1.25ghz 17" Neck, not the 800mhz neck.  For updated information about BOTH necks and how to tell them apart please see this post:
The Two 17" iMac Necks


UPDATE #2: I have posted a step by step guide for the 17" version.  See this post:
Guide: 17" iMac G4 to DVI 

Here is the iMac G4 17" TMDS to DVI conversion guide.  I have just finished this and can confirm that it works beautifully.  I have not yet seen sleep mode, but the image is otherwise flawless.
A couple notes about the table.  The TMDS # refers to the pins on the 30pin JAE connector that plugs into to the LCD.   There are 2 large cables in the iMac neck for the TMDS signal.  One cable has four colors (Brown, Blue, Green, Red) each of these cables divides into a +RED, a -GREEN, and a BLACK (GROUND/SHIELD).  So up to pin 14 refers to these wires with the large wire written first.  The other cable has 8 multicolored wires.  Of these only the white and black connect to the DVI cable.  The others need to be connected to a power source.  This can be an ATX power supply or an AC to DC power brick.  I am using an AC to molex adapter, I stripped to molex leads to get a 12V rail, a 5V rail, and a GROUND.  The panel's actual specifications call for 3.3V to the PURPLE, YELLOW, and ORANGE wires, however as I don't have a 3.3V rail, I used 5V which worked fine.  I don't know if there are any long term consequences to using too much voltage, but if given the choice I'd go with 3.3V.  So I connected the 3 VCC wires together (PURPLE, YELLOW, and ORANGE) and connected them all to the 5V RED lead on my molex.  The 3 Ground wires get connected together (BLUE, GREEN, and GREY) and go to the GROUND - BLACK lead on my molex.

******However, there is one more thing, the DVI adapter will require 2 more connections.  This does not involve the iMac TMDS cable at all.  A computer doesn't send a signal through a DVI port not being used.  It only turns on when it gets a signal that there is something connected - this is the Hot Plug Detect.  It takes voltage from the monitor, because the iMac panel is not supplying anything to this pin (#16 on the DVI) we have to supply it.  Luckily pin 14 on the DVI supplies voltage to the iMac panel.  So, you will need an additional wire and a 1Kohm resistor.  Attach one end to DVI pin 14 (this pin should already have the RED wire from the iMac connected - so there will be two wires connected to pin 14 on the DVI), splice the 1 Kohm resistor into this wire and connect the other end to pin 16 on the DVI (the hot plug detect).  You will ALSO NEED A GROUND.  One more wire must be connected to pin 15 on the DVI and this wire can go with the other ground wires (BLUE, GREEN, and GREY) to connect to the Ground/Black lead on the power source.

Now connect the inverter to the power source (detailed in a previous post) and your done!!!

Few tips:
    As long as your colors match up you do not need to open the monitor housing.  But here is where the TMDS pins get their number.  The connector on the left is a 30 pin JAE connector that goes into the LCD panel.  The pins are numbered left to right.





 I highly recommend using one of these.  This is a DVI connector.  You can also remove these from a broken graphics card or motherboard.  The TMDS female ends can be pushed onto the male pins.  It takes some finesse, but can be done.  The nice thing about this is  you can verify your connection before you solder.  This is the connector with 3 pins placed.

Below is again the DVI pin assignments (corresponding to the Right-most column in the pinout).  The middle two rows (TMDS 4 and 5 are not used, nor are the analog data areas).  Plenty of other diagrams of DVI pinouts are available online if this one is confusing.  I also wanted to add that this diagram is a FEMALE DVI connector.  If you are cutting a male to male DVI plug or using a MALE connector, it will be the mirror image.

 Here are a couple of shots it operational.  This particular imac had the front bezel removed.  I apologize that the connections aren't very clear.  I'll try to add some better pics of the actual hookup in the future.  I will probably not being completing this as an all in one - I'm reserving my supplies for use on the 20".  I actually have made some headway with the 20" inverter and I will post updates shortly.

I know many are eager to try this out.  As always, I'd be happy to answer any questions.