Saturday, November 27, 2010

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.

Saturday, November 13, 2010

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.