Analyzing a DirecTivo Problem

Our DirecTivo (Samsung S4080R), which we purchased new in 2005 (fan replaced in December 2008), is having an odd problem that I’m trying to intuit out before I call for service. Here are the symptoms and observations; opinions are welcome:

  • On at least two of the premium channels (537 Sho and 533 WHAM), after perhaps an hour of watching the channel, we start getting video “blurbles” (i.e., where the picture pixelates and resynchs), and occasional “searching for satellite”.
  • This behavior has not been observed on any non-premium channel.
  • This behavior has not been observed on any of the other non-DVR DirecTV receivers in the house (one RCA, two newer SD receivers).
  • I have rebooted the box, but the behavior returns.
  • I have tightened the connectors, but the behavior returns.
  • I have not been able to observe whether the behavior is specific to a particular tuner in the box.

Given that the problem is not on all TVs, I don’t believe it is a problem with the dish itself (i.e., I don’t believe there are cracked LNBs). The multiswitch was replaced in May 2007 with a Zinwell Wide-Band 6×8 switch, but that didn’t work well with the SD TVs, and was replaced again in November 2007 with a 3×4 Multiswitch. I don’t know if just one or two outputs on a multiswitch could be bad. It could be the wiring to just that TV, but then it would affect all channels, not the premium ones. Perhaps the decryption chip, which should only come into play for premium channels, is failing due to heat.

Anyone with a knowledge of Tivos and/or electronics got any ideas? Looking at the Weaknees FAQ, it could be a defective tuner or a failing disk drive.