OK GOT A KM-3O40 WHERE THE DISPLAY WILL NOT ADJUST ENOUGH TO BE SEEN IN REGULAR LIGHT . YOU CAN TURN IT WAY UP AND IT IS VERY LIGHT AND WHEN YOU TURN IT DOWN IT IS COMPLEATLY BLANK. HAVE CHANGED THE LCD DISPLAY (2JB45010 LCD OPERATION) AND THE (2JB94040 PARTS,PWB OPERATION TOP ASSY SP) WITH NO LUCK.

ANY HELP WOULD BE GREATLY APPRECIATED.

does the PCB you replaced have the cfl inverter components on it? If the cfl is not lighting up,then you would not get much display if any. I looked on the parts list and couldn't see which pcb had it.
The service manual says it is the right operation pcb that has those components. try PN 302BJ94030.

Hope that helps.

the pwb we replaced has the control for the contrast of the display on it

will look at the other board thank you