Good morning.
I hope someone has already gotten into this.

I own a Yaesu FT-290R that lately has been reported to produce a
distorted SSB modulation.

I checked with another receiver and I can unfortunately confirm that the
modulation sounds a bit warbled, fluttered, "bubbly" but still
comprehensible (say "3 by 9" RS report).

Apparently the problem worsens when the rig is operated at lower
temperatures (32F/0C or so). In low-power mode the modulation is
slightly better but still unacceptable.

FM output is OK. Output power looks fine too, at least there's an
increment between low and high levels.

Has anyone had this problem? Any cure?

Thanks,
pc