All,

I have acquired a Sony ICF-SW40 radio. The rotary tuning knob on the
side of the unit is faulty. When I rotate it in a given direction,
the frequency setting doesn't change in a linear fashion but hops in
indiscriminantly sized steps in either direction up or down. This is
true for all three bands. Hence tuning is very unreliable.

How is the tuning wheel coupled inside the radio?

Could this be an issue with excess dirt / lack of lubricant in the
tuning mechanism?

Has anyone experienced this kind of problem before and how was it
solved?

Thanks
SB.