Noise on Digitech rp2000

[fasardi]

Hi! I own a digitech rp2000 since year 2001, and i had some problems with switches and the expression pedal, nothing to worry too much. But now, i heard some fffshshhhhhh noise getting out of it, not only from the left or right output, i use the spdif output to enter to my delta 1010 to record some direct guitars and i get the same noise. I'm still able to play, but the noise is always there. Any things i should check out? could a factory reset do something?
Thanks a lot for your help, and sorry if i wrote some "tarzan" english, i'm from Argentina!