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