Like the other poster said, it could be your power supply or weak
connection. Also make sure your coaxial cable is not inducing something
into the power supply leads. Check those first. If not it could be an
instability in the power control loop. Maybe a weak filter capacitor.
See if the high power is set properly and the current drain is correct.

Bob D. wrote:

I'm getting a buzz in my audio using high power on my new Yaesu FT-8900R. It
only happens on high power after a warm up period. It happens even on a
dummy load, so it's not SWR related. Any known problems with this rig? Does
Yaesu have a 'problem' web page?




--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P