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Gil, make sure the 430 is putting out a good clean signal when it
goes to full power..not a self oscillation of some kind..The control
pot could be defective,,,also power out can be controlled from ext
remote connector,,,go to remote connector and connect a variable
voltage source..(+)to gnd...(-) to pin 6 ..apply -2 to -10 volts
,power should run from low to full power same as front panel
control.Let me know if I can help, I own a 430 and once did Kenwood
service work..good luck Harold W4PQW