Intermittent Buzzing noise from input jacks

I keep getting a periodical buzzing noise from the left jack of the two inputs. It buzzes, capturing the buzz if i record my keyboard into my MPC, and then disappears. Returning every few minutes.

Anybody had this problem before, and is there anything I can do about it?

Hi,

I have the exactly the same problem as you almost since i got my 4k new ,back in 2006.
It´s nothing to do with the suggestions given above.
My guess is that it´s the phono pre-amp cause when i use line input the signal is clean.
It´s really annoying though!

came accros this problem a few weeks ago. never expirienced the buzzing noise before so at first i was kinda shocked. disconnected both the cables, cleaned the tips on the xlrs and connected them again, solved the issue