Had an issue with my stock 11 inch Equinox 900 coil. It began to chatter incessantly and there was nothing I could do settings wise that would stop it. To verify it was the coil, I took it off the 900 and put it on my EQ 600. Same thing, started chattering and would not stop. Put the EQ 600 coil on the 900, no problems and no chattering. So, it had to be the coil. Sent the coil to Minelab and they determined it was a bad coil and they sent me another one. Has worked flawless so far!!