Sunday, July 29, 2012

Updates on 20" iMac G4 "PRO" Mod

The "PRO" iMac G4 Mod

I apologize about using the "PRO" moniker which along with "MINI" has become overused when referring to apple mods or speculation on future apple products.  I use it here simply to differentiate this mod from the very similar iMac G4 Sandy Bridge Mod.  This mod isn't really a "PRO", its really just different.  When I was putting together my previous mod, there were things I wanted to include but didn't because I was concerned it would alter the original appearance and function of the iMac G4.  I made the decision to keep that mod as faithful as possible to the original.  As such, the microphone, LED light, optical drive, and outward appearance were kept intact.  I had wondered how it would have turned out had I gone the other direction and after sometime, I have decided to find out.

I was hoping that Ivy Bridge ECX boards might be available by the time I started this mod, but to date I have seen only one: GENE-QM77 by AAEON which is currently cost prohibitive.  As such, I am proceeding with the same Quanmax KEEX-6100 I used in my previous mod.  This board has surpassed my expectations and as it was easily compatible with 10.7 Lion, I am hopeful 10.8 Mountain Lion will work smoothly as well.  That said, there was room for some improvements.

Preliminary Tests


For some reason, 4GB is listed as the maximum RAM on some parts of the KEEX-6100 documentation and 8GB on other parts.  It turns out that 8GB is the maximum and I have upgraded the RAM accordingly.


The top of the Dual Heatsinks
I had initially planned for a Core i7 Quad Core, but was concerned about temperature and power usage.  The highest wattage Pico PSUs were 150-160watt, but the native PSU supports 190watts.  Unfortunately, with the drive in place the native PSU does not fit.  In addition, the standard socket heatsink and fan were not adequate for the quad core, but a larger heatsink or cooling system could not fit.  As such, I used the dual core - i5 processor.

To use the Core i7 Quad, I simply need more space.  The optical drive will be eliminated.  This will allow for use of the native PSU as well as a more robust cooling solution.  I have described use of the native PSU in a previous post and this carries with it the added benefit of doing away with the power brick of the Pico PSU.  For the cooling, I have decided to fuse a passive Socket G2 heatsink with the larger desktop active heatsink pictured here.  So far, this seems to be a signficant improvement.

The KEEX-6100 with Large Heatsink/Fan


A Touchscreen

There are two accessories that I feel fit well with the iMac G4.  The first of these is a Touchscreen.  Those familiar with my blog may recall my cinema display mod which used a 5-wire resistive touchscreen.  While I loved the touchscreen itself, I did not love the resistive touchscreen.  It had a tremendous glare, took away from the LCDs image, and its responsiveness was less than perfect.  Also, incorporating a touchscreen into Apple's hardware has always been difficult.  Many other manufacturers have "wiggle" room.  These unused centimeters of space allow for a touch controller to fit.  They also allow for the touchscreen itself to fit in front of the display.  Apple tends to pack things in tight, making this much more difficult.

Optical, IR, Resistive, and Capacitive Touchscreens

In selecting the type of touchscreen to use there were two basic options.  The first option was using optical or IR touch which would have required an array and sensors within the bezel.  This would require moving the LCD further back with regard to the bezel.  The second option of resistive or capacitive (also Surface Acoustic Wave) used a glass or plastic panel that sits in front of the display.  As there is no extra room in the iMac G4's LCD housing this would mean either making the LCD itself thinner or having the touch panel sit flush with the bezel.  The decision was somewhat made for me as a result of the 16:10 20.1" dimensions required.  Modding a 19" 16:10 IR caused blind spots in the all too important corners and modding the 16:9 20" optical sensors to 16:10 caused it to barely function at all.  These methods have potential, but will require more experimenting.

I have obtained a 20.1" 16:10 capacitive touch screen from 3M that appears to function markedly better.  The largest negatives are its thickness and weight.  Because of its thickness, it will not fit in front of the LCD glass.  the active touch area falls within the bezel, the size of the touchscreen includes an inactive area that is on the outer portion of the panel.  Thus, it must go inside the bezel, outside the bezel, or the bezel must be modified.

Initially I thought about converting the backlight from CCFLs to brighter LEDs allowing me to shrink the diffuser inside the LCD housing.  The diffuser is a clear plastic piece used to spread the light uniformly.  Unfortunately I was not thrilled with the light distribution in some of my tests.  Again, this is certainly something that is possible and may be revisited in the future.  JeanLuc7 has done amazing work with conversion of CCFL to LEDs in his blog: 53 cent. (It is in German).  However, I decided to look to my older mods for ideas.

The Apple Cinema Display/iMac G4 Touchscreen Mod  used the housing from an apple cinema display.  This was done because at this time I did not know how to use the native inverter and the cinema displays would not fit.  Both the controller and the inverter fit within the Cinema Display's housing.  I then attached the resistive screen to the front of the cinema display and the iMac G4 bezel in front of that.  This was not an elegant solution as the touch panel protruded far in front of the LCD itself.  Even the touch wires were exposed and wrapped around the side.  To internalize everything, I decided to cut the inner part of the ACDs bezel allowing the touch panel to sit flush with the bezel.  This was a dramatic improvement.   See the ACD/iMac G4 Touch Improvements post for details.

Here are pics of a trial of a modded iMac G4 bezel using the same concept:
The Front
The Back
20.1" 16:10 LCD
 The bezel contains a white plastic with a clear plastic over it.  To this plastic tabs attach an "LCD Frame" to which the LCD is held in place by screws that come in from the side.  This causes the LCD to be recessed from the bezel in front of it.  Above you may see that I have cut away the inner (white and clear) plastic part of the frame.  Allowing the touch screen to sit flush with the bezel and thus "fit" within the iMac G4s LCD housing.  The problem is that the nonactive border of the touch panel and the metallic casing of the LCD itself will be exposed.  In the Cinema Display Mod, this was covered by the iMac G4 Bezel.  Here I am thinking of adding some type of thin strips in either the white color of the iMac or a gray/silver color that will go around the inner border sitting on top of the bezel/touch panel interface.  After all, I want this "PRO G4" to look different.  Any ideas would be appreciated.

An iSight Camera

In my current setup I use an iMac G4 and iMac G5 (both of which use an ACD controller to work), with a modern generation external mac mini.  The G4 has an optical drive in its base, while the G5 has an iSight which has been converted to USB.  What I've noticed is that having the camera on the G4 would have made so much more sense.  Being able to move the camera  as easily as you move the screen makes a lot of sense.  As I am modifying the panel already, fitting an iSight should be possible.  Several iSights may work, I have seen the 13" MacBooks camera used, but as I have and am familiar with the iSight from the iMac G5 and it appears to fit.  If you look at the modified bezel back picture, you may notice a small part of the gray LCD "Holder" is missing. This has been removed to accommodate the iSight camera.

I believe I'll be able to fit the small touch controller as well as the iSight Camera.  The problem is that the computer is in the base and I will need to wire this to the computer in the base.  While opening up the neck and adding additional wires is possible, it is not ideal, and we do have extra wires.

The Additional Wires

For USB we will need 4 wires.  As we have 2 items 8 total wires will be needed.

There are 2 wires the supply the LED.  One Red and One Green.  While the LED on the LCD is ok, I have been planning on putting an LED light elsewhere regardless.
The 2 LED wires
Although I plan on having a microphone, I will test out the consequence of placing it either on the top or bottom front of the base.  This will allow me to use these 3 wires intended for the microphone.  The Red, Black, Black wires of the microphone are pictured below.
The 3 Mic Wires
The Orange and Purple Wires are not used in this mod.  Although the Yellow is not hooked up in the picture it connects via resistor to the 5V VEDID, and is required to turn the monitor on.  Thus 2 wires are available.
Unused Inverter Wires
2+3+2 = 7.  As a result an extra wire is needed.  When I tried combining the ground or power wires for these two items, I ran into problems, so they must be kept separate.  Thus, an extra wire is needed.

Isolating the hot pink wire
I wanted to leave the LCD power itself alone if I could, so I decided to use the Yellow wire from the inverter.  My thinking was that the yellow wire (very low power) is required to turn on the inverter.  I stole this power from the DVI VEDID pin(5V via a 6.8Kohm resistor) and split it between this wire, the hot/pink (true VEDID wire) and (also via resistor - 1Kohm) the Hot Plug Detect DVI pin.  So I figured I'd move the split into the LCD case itself.  Isolate the hot pink wire and (leaving it connected) strip it with an X-acto knife and add a connection via resistor to the yellow wire that goes to the inverter.  This leaves me the entire yellow wire that traverses the neck to use for my USB hookups.

The Yellow wire being diverted
When hooking up the two USB devices without the monitor being on it works flawlessly.  However, when I turn the monitor on, I run into all sorts of problems from lousy response time to an occasional power drain warning.  Now, while I suspect the power drain comes from a connection grounding out, its the poor connection that bothers me the most.  I am concerned that the power running parallel with these wires in the neck is creating interference and that they may not be properly shielded to perform the task I am intending.

This leaves me with a couple options

1) Adjust which wires do what and try combining different combinations - here is whee I will start.

2) Use only one of the USB devices.  This would depend on how well they would function.  Obviously I'd lean towards the touchscreen.  But, if the touchscreen does not work well or if its weight alters significantly the motion of the neck, I would still like to incorporate the iSight.

3) Add a USB or mini/micro usb hub in the LCD case.  As it is very tight, I am not sure this would fit, but its worth a shot.

4) Replace the existing mic/led wire with a shielded Dual usb cable.  Maybe difficult to thread, but also a possibility.

An Unusual Problem

During this testing I came across an unusual problem that I believe is innate to the ECX board and native PSU itself.  Initially the screen would be black then light up when the computer was turned on.  When the computer would be turned off - there would still be a slight glow from the backlights.  Interestingly this seemed to be modulated by the yellow inverter wire where adding higher levels of resistance between this wire and the 5V dimmed this light, I could not eliminate it.  Disconnecting the 5V to the PSU or the PSU's 24V to the inverter turned off the light.

Native PSU's Blue and White Leads
At first I could not understand this as the 5V rails come from the DVI pin of the ECX board which was off.  I figured that some voltage keeps flowing through this pin, so I took 5V from elsewhere.  I connected this to the 5V from the SATA/MOLEX connector on the board.  However, I still had the same problem.  Then I tried a USB, again the same.  I realized that some voltage was flowing through all the ECX boards 5V rails as long as it was connected to the PSU, even if the board was off.

I believe this is a quirk between the native PSU and the ECX, as the native PSU is "always on" supplying 12V to the ECX.  The ECX requires only a 4pin 12V connector, it then down converts this to 5V.  So it appears there is always some power on the 5V rails. To solve this, I went to the 12V rails which are supplied by the PSU and not modified by the ECX.  Using the small 15watt 12V to 5V downconverter I have previously discussed and hooking the White/Blue of the PSU to the 12V Yellow/Black of the SATA/Molex via the downconverter, I eliminated this problem.

Wanted to mention this to anyone in case you are using my exact setup.

Connection to 12V Rail via Downconverter

So it appears I have some more work to do on this.......But I am going to put this project to the side for now, as I will explain in my next post.  Thanks for reading.


  1. I used a Core i7-2670QM (45W TDP) on my ECX-Board without native PSU.
    I disassembled the fan of the cooler because it works vice versa to the big 92mm.

    Temperatures are around 45°C and are increasing to at least 85°C while playing Counter Strike Global Offensive.

    1. Thats definitely warm, but not critical. Still, it does make me consider an ULV processor. Im not exactly sure what you mean about the fan. Did you take off the fan and leave it as only a passive heatsink, using the 92mm fan to blow air in towards the processor?

  2. I have 2 iMac G4 at home (a 15" and a 17"), I'm thinking about modding them. I want to replace the LCD and add a touchscreen. I have an old LCD from a toshiba laptop which is 15" and 1600x1200 (instead of the native 1024x768). I'm pretty sure it is LVDS. I'm thinking about reusing it and replace the CCFL to LED (thanks for the link you provided!) to avoid high voltage (is it a good idea ?). My question is about the capacitive touch screen. I can't really find where to buy these touchscreens, where do you think it would be not to difficult to find a 15" touch screen not to much overpriced?
    When this will be done I'll start to think about modding the base using an ECX board or maybe one these new "Next Unit of Computing (NUC)" when it will be available to give it a try.

    1. Personally, I think replacing the CCFLs with LEDs is a great idea. This is still on my "things to do" list. The problem for the 20" is its atypical 16:10 ratio. No 20" LED monitors exits in this ratio, instead you will see 20" 16x9 (non-HiDef 1600x900) and 21.5" 16x9 (Hi-Def 1920x1680). As you said, not having to deal with the high voltage inverter issue will certainly help. In addition, the thinner diffuser required by an LED backlight will allow you to fit a touchscreen overlay in front of the panel. But, you can not use all the TMDS wires for LVDS. TMDS works differently, and most of the red/green/shield wires should be changed. This isn't the end of the world, but opening up the neck and swapping out wires does increase the difficulty and chance of damaging the neck. As your screen has a 4:3 aspect ratio, it should fit, but you will need a LCD controller to drive an LVDS screen as well as an LED backlight converter.

      Although they have come down in price large scale (>10") capacitive touch screens are not going to be cheap. For instance on new egg, there are 4 touch screen 15" capacitive monitors for sale, the cheapest of which is $460 and the specs are otherwise very unimpressive. Buying from manufacturers as a consumer is tough as you are not ordering in bulk. You could try a sort of in-between like 3M. Here is a link to their capacitive touch systems selector, but they are not cheap.

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