Returning problem where most Premium channels can not be tuned in.(e.g most HBO, most SHO, other misc like SCI). Does not matter if I choose HD or non-HD channels.)

My suspicion is that there are a variety of signals or encodings for various generations of tuners, and this rarer type configuration may be de-tuned or turned off occasionally. The previous fix seemed to be out of the control of the local service people; I base that observation on all of the 'standard fixes' which made no difference, and how it started working a little while after the tech left,