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.

The Elusive All-In-One

Let me introduce you to my new favorite form factor: The Embedded Compact or ECX.  When I took this out of its box, even though I knew its dimensions, I was shocked at how small it was.  I do want to caution that everything with these boards is proprietary including its cables and proprietary = expensive.  So know what your getting yourself into.  I've seen these available in either Atom or most excitingly Mobile Core 2 Duo configurations as this one is.

For perspective I have included a picture with a metro card (credit card sized).  To demonstrate how small these boards are.  The have the same dimensions as a 3.5" drive, but they are also quite thin as the mobile processor fans are small and the ram inserts horizontally on the underside of the board.

In terms of features you can see the PCIe x 4 slot, a DVI/VGA/HDMI out.  However, there is actually an LVDS out as well inverter pins (yes the entire LCD conroller is embedded in this tiny motherboard).  So you could connect the LVDS cable and inverter directly to this motherboard without any additional hardware.  Now the question is can the native LVDS resolution drive the iMac's 20" screen? And does this solve the problem with the inverter for the 20" iMac - maybe?

The underside shows the RAM (4GB) in place (purchased separately) as well as a slot for a Compact Flash Card.  This I also find to be a fantastic addition.  I need all the space I can get and although I am not sure, I would be surprised is an embedded board was unable to boot from the compact flash memory. This could mean with a 64+gb card no need for a hard drive, no extra heat or power, and a much faster system.


Here is the 2.53 Ghz Core 2 Duo Mobile (Socket P Penryn Processor) and its very reasonably sized heat sink/fan.

This is the first board that I have felt makes an all-in-one doable.  I have never liked the idea of shoehorning a mini itx or mac mini into the base at an angle.  Plus I had extreme concerns about airflow.  I imagine this sitting above the dvd drive with the cpu fan around the same place as the iMacs original fan.  This board also allows incorporation of a dvd drive.  Although not necessary anymore, I always felt it was part of the iMac's charm.  In addition, if no other hardware is required that would leave the bottom for placement of a powerwave adapter (to use the original speakers) as well as extenders/ports to make the rear I/O look as original/professional as possible.  It does use a power brick, but I am certainly ok with that as no internal powersource = less heat.
Now I could find this board impossible to work with, it may not fit at the top of the base, it may require a hard drive.  I don't know, but keep this in mind the original iMac was an embedded compact motherboard, it only makes sense to use something along those lines.

I already know I can thread LVDS cables down the neck into the base with a replacement 20" LCD.  However, I could also try to splice the existing panel to DVI.  I'm not sure which way I'm going to go - but I am leaning towards LVDS (if the native resolution is compatible) as it is embedded onto the motherboard, thus will turn on/off with the motherboard etc.  For people interested in doing this, you will need extra LVDS cable.  The best place to get it is ebay.  I find cables used in flat screen tvs are usually longer and of more use.  Examples of LVDS cables from tvs are shown in the pic on the right.

The biggest problem I'm going to have is with that damn 20" inverter (I am not running high voltage cables through the neck again - too unsafe).  Unlike the 15 and 17" I have not been able to get it to work independently.  Although there are pins for the inverter on the motherboard, it is one short.  I believe there is some voltage difference involving orange and yellow that turns the inverter on.  I am hopeful that maybe by having an active dimmer hooked up that this may solve the problem.  Obviously using the native inverter with the motherboard would be option number 1.

Option 2 would be to locate some other aftermarket inverter that will work.  I have yet to find one that is "flat" enough to fit in the monitor casing, but I haven't looked for sometime.

Option 3 is something I have recently begun to play around with and that is led lighting.  I could try edge lighting the lcd glass, replacing the CCFLs with these superbright leds from environmental lights.  These work on a 12v dc line which can be supplied directly from the motherboard without need for an inverter.  This is a 6 foot roll.  They do come brighter however, this requires a 24v dc line.  If this is not bright enough, I may try led back lighting instead of edge lighting.

Option 4 is using the 17".  Although I'd prefer the 20", if getting the backlights to work on the 20" proves too difficult, I already know how to do so with the 17".  And would be quite happy with a fully all-in-one modernized 17" iMac G4.

I'd love to hear advice from people who have some know how with led backlights etc.  And as always I'd be happy to answer any questions.

17" Inverter Pinout/Instructions

To test pinouts I would recommend getting either a molex or sata to ac adapter such as this one:

By sacrificing an inexpensive molex splitter you get 2 12V, 2 5V, and 2 Grounds without having to deal with the hassle of an atx power supply.  It also comes with a handy on/off switch.  These are available from newegg for pretty cheap.  I would recommend getting an sata one if possible however, as that will give you a 3.3V line as well.

To get the 17" inverter to work you will need a source of power, the screen and inverter, as well as a couple 1Kohm resistors (mine were rated 1/2 watt).  Here is the pinout and connections on the right.

Interestingly I was unable to get the inverter to light without a resistor between the green and the 5V line.  I expected this with the purple, but not the green.  Also note that I am pretty certain the native power supply to the purple is actually 3.3V.  As it is simply an on/off I doubt the extra voltage will matter, but long term I can not say for sure.  If you have an sata power source you should try to use the 3.3V line and if it works I'd probably lean towards using the correct voltage.

As you can see I left the dimmer floating, there are various ways of making a dimmer, but it is not necessary as the backlights appear plenty bright by using this method.  Just as a reminder for those of you hooking up to a molex/sata power supply.  YELLOW = 12V, RED = 5V, BLACK = GROUND, GREY = 3.3V (only on sata).  There is also nothing wrong with using an atx power supply and its various voltages, I simply found this easier.

*NOTE: After hearing from a reader that the screen flickered with the Red line connected to 12V and stabilized when connected to 5V (and then confirmed by another reader) I decided to recheck it myself.  And 5V is indeed the correct voltage.  I then went and looked at my old notes which showed "Red - 5V".  I made an error when originally making this chart.  I apologize for any inconvenience and have updated the above chart.

Revisiting the G4

Part I:


So much for changing gears. I have taken a long break from the iMac G4 mods but recent developments have gotten me excited to revisit the designs. First, the excellent work done by the folks over at macrumors especially pgee70 who has solved several of the problems caused by splicing dvi directly to the 15" monitors tmds cable.  As well the original japanese modder who performed the first successful splice.  I encourage anyone interested in this mod to check out their work.  One of the most annoying components of this mod is opening the neck and the ability to avoid doing so would be a gigantic step forward.

Secondly - cheaper and lighter touchscreens.  Although most do not seem to share my enthusiasm for the iMac G4 as a touchscreen computer, I can say firmly that it is far and away the best design for a touchscreen computer I have come across so far.  I know companies patent everything all the time but here is apple's patent filing for a touchscreen imac courtesy of engadget.  Look Familiar? My touch screen 17" mod makes a fantastic kitchen / family room computer.  It functions as a small internet TV, video jukebox, and web browser.  Now we are seeing capacitive screens available at a reasonable cost.  However, the iMac does have a fatal flaw with touchscreens - they MUST be light.  Because all the weight is placed at the front of the iMac this often causes problems with "arm drift".  Especially with the weight sensitive 15".  However, new film-to film touch screens eliminate this problem as they are essentially weightless.  So, I will try the15" DVI splice mod, but I will also incorporate a film-to-film touchscreen.  My goal will be to not open the neck if possible and use only the extra wires (microphone/LED/dimmer) to connect the resistive screen to the base.  Although I have read that people have done the same with the 17" there is no pinout or instructions available online.  I know many people are interested in converting their 17" using this splice technique and I have plenty of extra arms and iMac components to compare and experiment with - so coming up and verifying a pinout of the 17' should be possible.

I will be posting a parts list for the 15" mod shortly, and will post updates as I move along.  I will try to work on the 17" pinout and guide as well, though will unlikely take this to a completed mod.

ADDENDUM: As you can see from my recent posts I have decided to bypass the 15" and focus on the 17 and 20" iMacs.  The 15" mod has been done several times and I believe replicating it won't really add much to the community.  Still, if you are doing this mod and need any help beyond what is available from macrumors and other sites listed, I'd be happy to answer any questions.

Part II:

Other newer developments include smaller form factors.  I have yet to complete an all-in-one - my 17" hides behind it a computer.  It is possible to shoehorn a mini itx board at the right angle into the base or a caseless last generation mac mini.  Despite this - I would be very hesitant to put anything hotter than an atom-ion combo in the base.  The G4 was designed as a convection cooled computer.  The airholes are located next to the exhaust fan and the mobo is otherwise surrounded by a heavy metallic faraday cage.  So there is NO air movement at the bottom of the dome.  However, some decent smaller form factor boards specifically the embedded compact have just come on the market.  Although they use mobile processors - a core 2 duo is would still make for solid computer.  Also, using the splice technique no monitor components will waste precious space in the dome.

The 20" still remains the toughest challenge.  While it takes only a power source and a few resistors to turn on the backlights to the 15" and 17" mods - I have never been able to get the inverter to work unless connected to the original iMac.  Because no aftermarket inverter is thin enough to fit inside the monitor casing - it has to go in the dome.  As a result, there are 6 high voltage wires that need to traverse a moving metallic neck.  It was because of this that I disassembled my original 20" mod.  I did not believe I had adequate shielding on the wires.  However, I have recently come up with a possible solution that I will be investigating in the next few weeks.  Thanks for following along and as always feel free to ask any questions.

17" iMac G4 LVDS Conversion - Video

Video of 17" iMac Mod

Here is a video of the mod in action.  I have connected it to a small mini itx computer running Windows 7.  As I said before, I do plan on getting a mac mini for this mod eventually.  I wanted to get a general sense with how the leopard user interface would work with a touchscreen, so I skinned the computer to look like leopard (using Rocketdock and Apple Icons).  The user interface works great.  Having the dock makes selecting programs easy.  With this networked computer I am only a few touches away from my entire home movie, picture, and music collection.  In addition, using Webtaps for firefox allows me to rapidly select videos from internet sites such as hulu.

To complete the look I am using the iMac G4's original keyboard (I like using the wired keyboard because I plan on concealing the actual computer, this gives me two easily accessible USB ports).  I have also added the magic mouse and the USB griffin powerwave adapter which allows me to use the iMac's original Orb speakers.

I hope that this blog has and will help with similar projects.  For myself, I have decided to next work on an ATOM/ION G4 Cube mod.  Similar mods to this have been done, but I think having a slot loading bluray home theater pc (capable of HD output) in the shape of an apple cube would look great in the family room.  Also, I hope to get back to a multitouch table that I had been doing some work on.  So one mod done and on to the next......

17" iMac G4 LVDS Conversion - Completed

UPDATE (11/4/11): Although not quite as worrisome as the 20" TMDS to LVDS conversion, I still recommend against using this method as high voltage inverter to CCFL wires go through the metal neck.  Please see my summary of mods or my 17" Step by Step Guide for an easier, more stable, cheaper, and safer way of doing this.

Original Post:
I actually get to write this post from my completed mod!!!! (Well from my laptop cloned to my monitor, but close enough).  I think it came out great.  The image is clear and bright.  The touch screen adds some weight, but there is no significant "monitor drift".  It took a while to get the touch screen working and calibrated, but it works fantastically.  In most situations I think touch screens on desktops make little sense, but for the G4, the ability to grab the screen move it towards you and  tilt it up makes it extremely fun and useful.  It's not multitouch, but that's OK.

This is the end of a really fun experience.  I think this is the perfect compromise between my two other mac mods and I do have to say that I actually think I prefer the proportions of the 17" vs. the 20".  For anyone debating - after doing both - I would strongly recommend the 17" over the 20".  The components are MUCH cheaper for the 17".  Also, 6 backlights in the 20" leaves a lot of voltage to travel through the neck.  The 17" allowed me to add much more shielding to the cables and made the mod significantly more stable and I still had enough room for a touchscreen.

I'll add a video in the near future to demonstrate the touch screen functionality and the mod in general.  When I became interested in doing this - I was shocked by how many others had similar ideas and I hope that this blog has helped and inspired others that are attempting to do a similar thing.  It is very doable and there is nothing that you can buy in a store that comes close to a one of a kind device that you build yourself.  That reminds me I'd like to thank fellow iMac G4 moders Blugray and MacOdyssey whose blogs and posts inspired me and without whom I never would have been able to finish (or even start) this project.

I have to admit though its a little weird to see Windows on the iMac G4.  I may have to get a mac mini for this computer, I'll just have to hide it under the desk .... ;) As always, I'm happy to answer any questions.  Good Luck!!