Symptoms: Second speaker has scratchy sound, and cuts out
when adjusting volume.

Cure: Requires replacement of potentiometer, or alternatively 
use of contact cleaner.

Identical (note: untested) pot appears to be a 10K 2 gang logarithmic
pot, manufacturer id: PDB182-K425K-103A 
(Bourns).

Detailed description:
10k Ohm 2 Gang Logarithmic Panel Mount Potentiometer None 1 Kierros Carbon 0.06W PC Pins