[Radioroslyn]

Here's the quick rundown. Your model 86 is a TRF receiver which means that it is not a superhetrodyne. It uses several stages of radio frequency amplification, Detects the signal (converts the rf signal to an audio signal), and then it is fed in to the audio amplifier.
As I remember to knob on the left is connected to the antenna and will tune the antenna circuit a bit. Knob on the right is the volume control.
The LOC connection can be used for an antenna by connecting a jumper from the LOC to the ANT posts. Note the LOC post is connected though a condenser straight to the AC cord. If this condenser is bad you may get a nasty shock or damage the antenna circuit
This set covers the AM broadcast band (1929) which goes up to 1500kc. No shortwave. The hum adjust balances the filament current on the three rf amplifier tube (#26's) Should be set for minimum hum. Diagram can be found here:
http://www.nostalgiaair.org/PagesByModel...029653.pdf
Suspect parts would be #'s 22,26,12,17,7. Replace #33
Terry
ps forget the guitar thing.