[Hallicrafters] SX-28A Oscillator Interference

[jim]

I have a SX-28A that receives on all bands, but produces a high pitched 
tone or oscillation every few mhz as it is tuned.  Stronger stations 
over-ride this.  I've noticed the RF Gain contol and Antenna Tuning 
control affect the noise just like it would if it were coming in from 
the antenna.  If I disconnect the antenna, the tone is still audible but 
not nearly as high in intensity.  I'm guessing it needs aliignment 
because it looks like a previous owner has adjusted the slugs in many of 
the coils and they seem positioned way far in to the coils in some 
cases.  I'm told the RF deck was recapped and the low value resistors 
there are within spec.

I think this set must have been used pretty heavily because the main 
tuning shaft wobbles just like a bearing in bad and I had to replace 
both the toggle switches.  The fly wheel wobbles too.  Stilll, it sounds 
pretty nice and is more sensitive than I thought it would be.

Has anyone got ideas what might be causing the oscillation noise?  Maybe 
parts placement or coupling?

jim, k7rgl