I have had a Yaesu FRG-7700 receiver since about 1982. It's developed a
problem recently in that the frequency shifts all over the map when you
touch the tuning dial. There is no way to tune to a specific frequency
because the tuner and the dial display are so unstable. Anybody have an
idea what may be causing this and how to fix it?

BTW, I haven't changed the backup lithium memory battery since I got the rig
20 years ago -- and all the programmed memories and the clock still work!

Thanks in advance for the help.