[morzh]

Also, in my 38-15, which is the same radio with a SW scale, the first tube is 6A7 and it is often enough acts funny when getting old. Mine decided not to work on half the SW scale. And not it is only the oscillator but also the RF amp, so if it is weak (and they are more often than not have very weak triode section while the generator section is fine) the sensitivity goes.

Plus what others said.