HAHA yeah j-loreen is correct not all of us have kids(or want kids.. damn they go from potty trained to potty mouth these days.. is it just me or are kids bad these days??).. lol
now if i have your question correct then you have a hasbro obi FX lightsaber(NOT the cheap plastic toy saber from walmart) that originally has a fixxed blade and ALL metal hilt about 45" total length, 1" blade, movie sounds, takes 3aa or aaa batteries im not sure on that model but takes 3 of them<-----
If thats the correct one then Yes you can convert it to LED, still using the stock on/off switch AND use the sound board to drive(run) the LED.. it will remain identical to its original replica appearance with the addition of a blade screw. heres a link to what i THINK your trying to do
http://forums.thecustomsabershop.com...ead.php?t=5729
*hint always check the pictures to confirm you have the saber the conversion tut is about*