The Holy Grail

Excerpted from the Applefritter FAQ

Q: How do I turn this laptop/iMac screen into a monitor?

A: Put simply you don't. Whilst it is possible to use a laptop (or iMac) screen as a monitor it takes a large cash investment and a good understanding of electronics. If you are lacking in either of these departments don't bother, buy a cheap LCD with VGA connection on eBay instead.

If you really want to know more about using a laptop display on another computer then do a search of the hacks sections with 'holy-grail' as your keyword. You can also try visiting Earth LCD for more info regarding the required convertor boards.

The LCDs in iMacs fall under the "laptop screen" category as Apple designed the iMac's onboard video circuitry to drive the LCD directly, like laptops do. There's no intermediate controller to which you can simply feed a VGA or DVI signal.

Here's one of the best explanations of why using a laptop LCD for a monitor is a difficult project I've seen so far, courtesy of Eudimorphodon:

Laptop displays simply don't speak the same language as CRT monitors, electrically speaking. It requires a complex wad of electronics to turn output meant for a CRT into input suitable for an LCD, and that wad of electronics is referred to as the 'controller'. You won't find a controller you can salvage in your laptop anywhere, because it 'speaks LCD' directly, and thus doesn't need one.

It's not just a matter of pasting wires together, which is what everyone wants to think. Those controllers sell for anywhere from $150 to $300, and for most installations require custom cables and power supplies which may well run you another $150.

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I've done it by replacing the monitor for the 17" iMac

By replacing the monitor with a standard LVDS lcd and wiring through inverter extensions and an elongated LVDS cables through the neck you can mimic the look of the iMac G4 perfectly. You can place the monitor components in the base and use it as an external monitor. Hooking it up to a mac mini or any source you choose. I have detailed the process I used at:

http://dremmeljunkie.blogspot.com/

DrBunsen's picture

Respect for your excellent ca

Respect for your excellent casemod, jberg, but this FAQ is in regards to using the LCD panel itself. All you have used is the housing. It's not really relevant to this page, cool though it is.

The Holy Grail - Updated

Keep in mind the iMac G4 is different than most laptop screens in that there is a Texas Instruments chip inside which converts a TMDS signal to LVDS. Since DVI uses TMDS signaling (what I didn't even realize previously) - they've done most of the work for you already. All you need is a power source for the LCD and the inverter. (Although I have not been able to solve the 20" inverter). Here is the pin out for converting the two different iMac 17" necks to a standard DVI as well as powering the inverter:

http://dremmeljunkie.blogspot.com/2011/03/two-17-imac-necks.html

For most standard laptop screens, a converter or LCD AD would be needed.

The Holy Grail

Although it has taken some time, I have finally figured out how to use the native 20" iMac G4's housing, inverter, and LCD screen. This mod does require altering the wires that pass through th neck and uses the LCD controller and power brick from a 20" apple cinema display. This is used to power the screen and inverter. In this mod the LCD is hooked up to a core 2 duo ECX board in the base replacing the native motherboard. See below for details.

http://dremmeljunkie.blogspot.com/2011/05/imac-g4-20-all-in-one-ecx-mod-completed.html

Re: The Holy Grail

I have been contacted by many people interested in this mod, but who aren't sure if the have the technical skill required to do it. I have posted a Step-by-Step Guide of the 17" version of this guide that takes you from the iMac G4's LCD and inverter cable to a female DVI connector and male molex connector for the power source. Just plug the molex in and a DVI cable in to a source/computer and you are set. This method is "solder-less" though for stabilization soldering or heat shrinking is recommended. This uses the wires as-is in the neck - so opening of the neck or rewiring is not required. This guide can be found here:

http://dremmeljunkie.blogspot.com/2011/08/guide-step-by-step-17-imac-g4-tmds-to.html

In addition, I have finally figured out the 20" inverter (though the higher power requirements don't make it quite as easy as above). Now, the native 20" LCD can be converted to DVI, again without opening the neck. All you need is the proper power source, some extra wires, the proper DVI connector, and some resistors. A guide will be coming, but some info on this can be found here:

http://dremmeljunkie.blogspot.com/2011/11/20-imac-g4-genuine-mod-inverter-solved.html

I hope this is useful.

unknown1's picture

Re: The Holy Grail

This is pretty amazing stuff. Anybody try it with the Aluminum iMacs? I read somewhere the 21.5 and 27" have such capability built in, I have a 20" I don't plan on upgrading soon. Any chances?

EDIT:

Here it is:
http://www.cultofmac.com/20355/video-27-inch-imac-in-action-as-external-monitor/