If you don't mind losing your keyboard, (I don't think that you will), Do all this with the power disconnected.
Here is a link to the service manual which will help you to gain access
(click on image to enlarge for better viewing)
Hi @adolfoab59 ,
Think I got it wrong. I forgot about the diodes in circuit.
You have to split the 16 wire cable at one end between CN4 and CN803 into 2 halves. Wires 1 - 8 and wires 9- 16
If it is a flex cable with bare ends you may be able to gently disconnect the cable and then separate the cable into 2 halves at one end so that you end up with 1 x 16 cable at one end and 2 'separate' cables at the other end 2 x 8 wire.
Insert the 1 - 8 wires back into original position but reverse it so 8 is into 1 and 1 is into 8 and everything in between also moves as they are still joined i.e. 7=2, 6=3, 5=4, 4=5, 3=6 and 2=7.
Hopefully there is enough length in the cable to do this. Then do the same with wires 9 -16 i.e reverse it so wire 9 is onto 16 and wire 16 is into 9 etc.
Basically flip them both over over with a twist and re insert.
What you will now have is wires 1-8 at one end = 8 - 1 at the other end and , 9-16 = 16 -9. Suggest that you perhaps might do this at the CN4 end of the cable into the main pcb.