Hi, I also had this problem about 13 months back, it was traced to a faulty DSP on one of the boards. I got it fixed by line 6 in the UK. The same fault has now returned I contacted line 6 in the UK who have told me they no longer make any spare parts the only spare part they can get here is a new speaker. I contacted about 10 Amp repair companies who said they would not touch Line 6 stuff. So my beloved LD150 is destined for the scrap heap.