J creating a hiss?

[cyprus]

So my Ibanez SR800 seems to have developed a hiss from the J pick up that goes in and out. It sounds like my phone line on a rainy day (if anyone knows what that sounds like).
I've opened it up, poked around inside, unscrewed and adjusted the pick ups, used different cables and amps, and replaced the battery, yet NOTHING I do seems to make it better or worse. I'm at a complete loss.

Someone help me...?

 

[cyprus]

Okay, it seems like it only does after its been plugged in for a while. I was at practice today, and for the first hour or so it sounded fine. Then out of nowhere it picked up again.

 

[David Jayne]

If your SURE it's not your amp, it's the preamp in the bass. Electronic components are required to generate hiss.

 

[cyprus]

Yeah, I was afraid of that. Haven't the slightest idea of how to go about fixing that.
Was thinking of spraying some contact cleaner in there. Anyone know if this could cause any harm?