|iMac G4 Neck with Cinema Display Wires|
2) Do not put more/thicker wires into the neck than it can hold. Just because you can get it through the holes does not make it a good idea. When you overcrowd the neck, you'll start to hear grinding and some wires will wear down as they are pushed into the hinges of the neck. The iMac G4 has 4 wires that go through the native neck. When you replace wires, take out what you're not using and aim to have about the same "volume of wires" as the native neck comes with. To get wires through the neck all you have to do is push a wire that is already through backwards and tape about 1/2 an inch of the wire you want to get through to that wire and pull it through.
3) When you can't get a signal replace the black wire. I have heard from many people who can not get the 17" DVI hack to work. I know what the problem is - its the black wire. If one wire isn't touching then there is no signal. Too much solder on these wires causes problems. Even if you get a strong signal on the mutimeter, crosstalk can result in color changes, flickering image, etc. The wires are simply too small to reliably work with. Give it a shot and try to spare the pins that are attached. But, if you need to - replace them. Replace them with what you may ask. I used an apple cinema display's wiring here, but these are no different than any TMDS cables and the easiest place to get TMDS cables - take a DVI cable and strip it. You will find 4 wires that have three wires bundled within them, these are the same as the 4 wires within the iMac's black wire. Solder the pins to the top and you're set. Even though it will be four wires to one, they are thinner and if you need remove the led/microphone wire go ahead and do it. For my current mod, I have repaired problems with the black cable numerous times, I finally decided to replace it, with the apple cinema display's wires and haven't had a problem since.
4) Get rid of the Torx-6 screws. These are the most troublesome screws I have ever worked with. On the bottom of the 17" and 20" iMac G4's monitor housing you will find 3 screws that require a Torx-6 screwdriver to open. These are the screws that keep the monitor housing closed. I have never seen screws that strip easier despite using the appropriate tool. 6 points on a tiny screw is very close to a circle and once you start stripping it - its already too late. Chances are good that you may have to open up the monitor housing again at some point for upgrades, repairs etc. Act preemptively and replace these with small phillips screws - it will save problems later.
5) Want an All-In-One? Consider an 3.5" ECX or other small form factor board. Although mini-itx or a mac mini motherboard are the most popular choices neither of these is ideal from a size/heat perspective. ECX's can fit at the top of the dome in place of the native HDD where heat won't be as big a problem as it would with a mini itx at the bottom of the dome. They don't require an atx power supply and come with a variety of additional options including PCI-E mini or x4, Compact Flash etc. Processors range from Atom to ULV Celeron to Sandy Bridge Core i processors. This allows you to keep the full drive if you want and allows room at the bottom of the dome for ports at the back. Although not nearly as expandable as a mini-itx mobo, with such limited space in the dome, this isn't likely to matter.
6) Do not sacrifice stability for power. The mods I post don't include many mods which failed. Most of these initially worked but failed because I tried to force things. If you have to use all your strength to push your mod closed to screw it in, it will not last. If you cram things in between the motherboard and the air holes, your board will overheat. One mod I did post that was going to fail was the 20" TMDS to LVDS Conversion. Keep expectations in check. If you have a 17" monitor running at 1440x900 you don't need SLI or Crossfire. Having it turn on and having a critical problem like this is worse than it not working at all. If it doesn't work you can at least start troubleshooting what went wrong, these problems like the 20" TMDS to LVDS usually mean complete redesign and many of the parts have to be repurposed or replaced altogether.
Hope this helps.