Finally unboxed this after two years only to find that when I connect a cable to the sub out jack the right front channel goes dead. This happens even if it's just a cable with nothing attached to it. Checked cable to sub (as well as open end cable) and no sign of a short or resistance. Didn't use a sub before so not sure how long this has been going on. Know this is old technology but for my room will fill my needs. Any idea as to what I'm missing?? Thanks in advance!!