Yep, the flex cable carries both the backlight power and the video data: the two different types of signals are then split in two different cables, the one coming out of the blue plug goes to the motherboard and it's the same cable non-backlit portables use (with the difference, if I've understood the diagram correctly, that in the non-backlit the other side of the cable goes directly to the LCD assembly, with nothing in between), while the other goes to the inverter.
I'm not sure if we have the "motherboard-end" video cable, but I think we have!
The trouble here is that the two of them join in the same flex cable, so from what I've understood we should have two possibilities:
1) Reuse the flex connector on both sides (LCD and middle board) and connect a new flex cable. Since the cable actually splits in two, trag's idea to use two flex cables one next to the other sounds good and feasible, and it would have the benefit to avoid desoldering as much as possible. However, judging by the pic I'm not sure whether the flex cable goes into a plug in the middle-board, or is just part of the middle-board itself: in the first case a replacement would be easy, but in the second it'd become non-trivial.
2) Make use of CN1 header to solder a normal socket for a ribbon cable that carries both signals and then connect the cable to the middle-board by soldering each wire to its corresponding pin. This sounds like a lot of work, especially because we'd have to determine in some way which wire goes to which pin to avoid making the wrong connections; however, depending on how the middle-board is actually made (I haven't had a chance to see it in person, since I've directly delivered the portable to ferrix's place), it might be easier than adapting a flex cable on that end.
A third way that could be possible would be to reuse the two-flex idea of the first possibility, and then get a plug for each cable and solder that plug, running some wires, to the middle-board (that is in the case the flex cable is actually part of the middle-board, and not just inserted with a socket).
I'm not sure if we have the "motherboard-end" video cable, but I think we have!
The trouble here is that the two of them join in the same flex cable, so from what I've understood we should have two possibilities:
1) Reuse the flex connector on both sides (LCD and middle board) and connect a new flex cable. Since the cable actually splits in two, trag's idea to use two flex cables one next to the other sounds good and feasible, and it would have the benefit to avoid desoldering as much as possible. However, judging by the pic I'm not sure whether the flex cable goes into a plug in the middle-board, or is just part of the middle-board itself: in the first case a replacement would be easy, but in the second it'd become non-trivial.
2) Make use of CN1 header to solder a normal socket for a ribbon cable that carries both signals and then connect the cable to the middle-board by soldering each wire to its corresponding pin. This sounds like a lot of work, especially because we'd have to determine in some way which wire goes to which pin to avoid making the wrong connections; however, depending on how the middle-board is actually made (I haven't had a chance to see it in person, since I've directly delivered the portable to ferrix's place), it might be easier than adapting a flex cable on that end.
A third way that could be possible would be to reuse the two-flex idea of the first possibility, and then get a plug for each cable and solder that plug, running some wires, to the middle-board (that is in the case the flex cable is actually part of the middle-board, and not just inserted with a socket).