Digital Arts Final Installation

 I regard the iMac G4 as the most beautiful personal computer ever produced. I thought it tragic that such a work of art should slip into obsolescence and set out to revitalize it with modern technology.  My goal was to create a fully functional, modern computer completely within the confines of the original iMac all-in-one concept; everything contained within the unaltered body. Functional data ports, single power cable, etc.

Because of the limited room inside the computer, Apple didn’t use off-the-shelf components. Almost everything (including the display) was custom made to work with only those components. The culmination of four months of research, experimentation, and error, the most difficult part of this transformation, the display, was finally completed. The display can now be attached to any modern computer via a DVI cable. 

To complete this project, I constructed a custom power supply and completely rewired the display. To do this, I taught myself the finer points of power supplies, the inner workings of displays, LVDS and TMDS video signals, high voltage CCFL backlights, and spent a lot of time troubleshooting obscure electrical issues to which nobody seems to know the answers. 

Although the project was completed for a Digital Arts class, this is a personal project I first began thinking about after the iMac G4‘s discontinuation. I kept a blog of the entire process here. 

Final video displayed on computer during installation: 

Display: Complete

Well, after making the problem substantially worse, I ended up getting everything working perfectly! It turns out I did have a few of the polarities switched on the TDMS Data lines. That's what I get for trying to do this sort of thing at 1am. Anyway, everything seems to be working perfectly now!

So now, on to the Mac Mini part of this... sorta. I don't know when I'm going to actually get around to spending the $600 on a new mini for a computer I'm probably not going to use that often. Needless to say, I still want to do it, and if nothing else, I can use this as an external display for my laptop (when I'm not using my 20" Cinema Display?)

So Close!

So I replaced the black cord, cutting it right before it gets to the connector going into the LCD display. I had quite a hard time getting the 4 groups of wires needed for the 17" through the neck, but after an hour or so, managed to pull it off.

Once I got everything wired back up, I hooked it all up and turned it on. The good news is, no weird signal interference. The bad news is,  I think I mixed something up...

It's straight to the multimeter in the morning.

Backlights Pt. 2

Well I got it working. The problem was that I had both of the 5V via 1Kohm resistor lines going through one resistor. I split it, used two resistors and it came right up. 

However, this revealed the fallowing video signal issues:

Backlights Pt 1

As you can see, I had a little bit more success today. I used my makeshift power supply and hooked up my inverter using JBerg's pinout with the exception the red line had to be connected directly to the 5V line instead of the 12V line which created a flashing backlight that I turned off really quickly.

The only problem is the backlights seemed to be on their lowest setting, which I should be able to fix by adding a voltage to the Orange floating line.

Update: I applied the 3.3V (3.75V actual) to the Orange floating pin and the screen got infinitesimally brighter, but hardly enough to notice. I am now stumped. My only theory is that 3.3V produces the dimmest light, and as the voltage drops, the light gets brighter BUT if there's no voltage at all, it defaults to being super dim. I know very little about this stuff, so it's just a theory. 

Update 2: I added an LED to the end of the positive line, creating a voltage drop to about 1.5V. This still had no effect, although, I can't be sure that should even work in the first place. :-/

DVI Part 2

So, thanks to JBerg's most helpful and correct comments in my previous post, I indeed had my wiring all messed up. Because the pinouts are created using the female plugs, when you're wiring to a male plug, you have to line it up with the pinout from the back. I had no idea.

Pinout for 17" iMac G4 Screen to DVI

So I started fresh, Unsoldering all the wires from the DVI cable and soldered them back into their correct spaces. I also took some time to create a hopefully very intuitive pinout for the model of screen I had (using the info JBerg gathered)

After it was all said and done, SUCCESS!!! My backlights still aren't hooked up, but as you can see, the picture is coming through crystal clearly! This is very exciting

DVI Part One

Once the new screen arrived, I got right to work on DVI solder prep. To start, I removed the shrink wrap holding the two video wires together and used a pocket knife blade to carefully fold back and remove the thin metal housing.

Then I used the same blade to pry up the plastic tabs on the connector and free the little golden cable ends.

Because the DVI Cable is so large in comparison to the hole at the top of the iMac's dome, it's necessary to feed the neck wires into the dome and reattach it to the neck. If you use the two black screws, you won't have to use the white plastic cap that will force each of the four wires off in a different direction and shorten the amount of cable you have to work with. Just make sure you skip one screw hole so you can fit the white plastic cap back over the top when you're done.

Pinout for a standard DVI cable.

Then I got to soldering. For the most part, everything went really smoothly. However, there were a few peculiar things.

I talked in my last post about the shield wires and how they correspond with the shield wires in the neck by not having any insulation on them.

Well, because this is only a 17" monitor, it only uses 3 of the 6 possible TDMS data triplets (pair of wires + shield). The first three coincide perfectly with the red, light blue & dark blue triplets.

JBerg's Pinout of the 17" iMac's screen
(note: There are two possible configurations.
This is mine. See JBerg's blog post for more info)

But the final triplet (marked on JBerg's pinout as RxC and on the generic pinout as TMDS Clock, presumably the same thing) uses the DVI Pins 22, 23, 24 which are correct as far as the pinouts go, but not from what is actually showing up on the connector.

On the connector, the shield wire (Pin 22) is not looking like the rest of the shield wires on the cable, even though it's being connected to a standard looking shield wire from the iMac's cable.

And then, pin 24 (the TMDS Clock -) wasn't even a wire on the cable. I had to pull another wire from the cable that wasn't being used and solder it to the connector. That was very strange.

So I finished the DVI cable, fallowing the pinouts above.

For the power cables (grey, green, blue purple, yellow & orange), I rigged up a detachable connection using the connector from the iMac's inverter and some little pins. I attached the three positives (purple, yellow & orange) and three grounds (grey, blue & green) to the connector end. On the other side, I jury rigged some pins and attached them to a 5V @ 1 amp AC wall adapter.

At this point, I had the DVI cable all made up and ready to go. I figured I'd give it a shot without bothering with the backlights, just to see if it worked. Of course, it didn't. Holding a flashlight up to the screen, there wasn't a hint of an image.

The only promising thing was the my MacBook's screen went blue for a second as it does when you connect it to an external monitor, but when it came back, it didn't give any hint of an external display... :-/

Time to call it a night though.