Steve, did you ever figure out this behavior? My R-4A BFO has identical symptoms to yours. I fixed it by adding a 1K resistor to pull down the Vcc on Q6, but why does the transistor oscillate at 6V but not at 10V Vcc? I didn't check every component around Q6, but they don't look cooked. It was puzzling to have to park the mode switch halfway between AM and SSB to get BFO.
?
Dave
