On my Kenwood R-5000 shortwave receiver, I solved the disappearing frequency
display and associated audio
problem by replacing the original approximately 20-year old internal
battery. The displaying display is commonly called "dots" as all of the
numbers are gone leaving only dots in their place. I removed the original
soldered battery and replaced it with a battery holder and a standard Radio
Shack lithium battery. If anyone is interested, I
will provide upon their request step-by-step instructions including part
numbers for the battery holder and battery, etc.