I am getting a buzz from my new 6300 on 10 meters when I transmit over 40 watts. It sounds like 60 Hz relay chatter. All the other bands are ok. Same symptoms with the antenna tuner on or off, into a dummy load or not. If I keep it below 40 watts I can run my amplifier without any problems which leads me to believe it is not a RFI issue. Power supply is a 35 amp Samtec. Any clues?