Several years ago I bought a Series II and DS-5R from a person who had not used it at all since built, approximately 10 years prior. I had a problem with the DS-5R only putting out one pickup in mono. Upon advice, I began exercising the mono/stereo switch on the DS-5R. It literally took over 1200 "switches" to get the unit back into normal operation. So, while 50-100 exercises will normally bring things back to life, if your DS-5R wasn't used by the previous owner for whatever reason, don't give up as it may just take a few hundred more...