Interstate home equipment 68F volume cuts off

my interstate home equipment model 68F radio works great and sounds good, however when i play the record player it starts out fine and then the volume cuts off half way through playing the record.  if i turn it off and let it sit for a while and try again it sounds good and then cuts off.  where do i start trying to repair this.  does it sound like a capacitor or coil?  the cartridge and needle have been replaced

any hints would help

thanks