hi roger...i've been running a 6100 w 7091 controller for just obver 3 months now...all of the sudden one day it begins squeeling constatnt and very loud(the driver that is) i haven't tried to mess with it yet i wanted some advice as to what to look for and what to do...i'm not sure what caused this, or what to do...nothing has changed since ive placed the stream in the tank... i did notice that when i plugged the unit back into the wall after a few days to see if it was just a fluke the leds indicating the 2 various "speeds" began fluttering back and forth when the squeeling redsumed... thanks for your time