Well is it one of those dc coupled all through jobbies, if it is, then the
fault could be anywhere after the volume circuitry!
I had one of those Memorex branded tuneramps like this and it ate power amp
modules until, one day, the fault was in the protection circuit and it
welded up the speaker voice coil and trashed the amp completely.
Moral is, be very careful if you do not exactly know where the intermittent
bit is as something else will blow it all up for you courtesy of Mr Murphy.