strange noise from monitor

[jeam25]

Hi ...

this is the thing a friend of mine gave me a pair of evente tr8 active monitors because he wasnt using them but there is a problem with one of them. when you play music they sound good but when nothing is playing trough or lines arent conected then one of them.start to.make a static crack and pop.sound . it. sounds like when a guitar jack is broken but continously until it disappears itself.. i disasemble all the speaker ..check for any soldering problem . checked the volume pot . checked the power.switch
with no luck.... does anybody has had this speaker problem ??? and how to.fix it ???

thanks