Tuesday, January 25, 2011

Wiring the Neck

5pin connector
Cinema Display TMDS
 To wire the neck there are really two choices. 

OPTION 1: You can replace all the native iMac wires with the apple cinema display wires.  The advantage of this is that you don't have to solder the very small wires.  I simply removed the tmds wires (using a safety pin) from the JAE connector and 5 pin connector put them through then reconnected on the other end.  Only on the 3 wire power cord and the 4 wire USB cable did I have to cut off the connector and resolder at the other end.  However, getting the wires through is a huge pain.

TIP: Put the wires through the base first because the DVI connector is too big to fit through the opening.  so once you solder its too late.

To open the neck I again used a taped together mini screwdriver set.  It is not difficult once you get the first turn done.

So open and replace the wires.  (I'm using a neck from a previous mod - so the wires pictured may be unfamiliar).

Getting the wires through can be very difficult.  My advice would be to just bite the bullet and take the spring off its moorings put the wires through and then get it back on once completed.  Sometimes using a small wire to put through then wrapping around the actual cable and pulling through can help.

OPTION 2: Hybridize with the native iMac wires in the neck.  There are the 4 triplet pairs which carry the TMDS image (This is the top of the TMDS connector pictured at the top of this page).  The wires at the bottom of the image actually come from the control board so do not need to go through the neck.  There is an additional 5 pin connector (pictured above) that comes from the DVI and goes to the control board.  Although I haven't verified I suspect these are the hot plug, vedid, clock and data edid, and ground wires.  Although these are a slightly larger gauge than the wires in the iMac gray wire - they should carry the signal fine.  (you will need only 5 of these wires).  The iMac's inverter cable should work fine to carry the USB signal.  Unfortunately the power cable (and its 3 wires) carries 24V and none of the existing wires are adequate.  However, you do not need the microphone/lcd light cable, you can remove it.  This leaves room for the Cinema Display's power cable.  Like the above option, you do have to cut and resolder the cable.  The only one I'm not 100% sure about is the smaller gauge iMac gray wire carrying the wires from the 5 pin connector.  If that doesn't work, I plan on using the inverter cable to carry that signal and will replace the gray wire with the USB cable from the apple cinema display.  Below is the resealed neck with the Cinema Displays cable in place.  Of note, be careful how much cabling you leave on the monitor side of the neck.  Its still a tight fit in the monitor housing.

Getting through the one cable in place of another is not difficult.  However, the challenge is that it will require soldering on both ends.  So the tiny TMDS signaling cables 4 x 3 = 12 will need to be soldered on both ends = 24.  The five 5pin connector x 2 = 10.  The USB x 2 =8.  Its certainly doable and I will post when this method is verified.

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