The TU-DST50W was Panasonic's first DTV set-top box. It outputs all native ATSC formats (480p, 720p, 10080i) through YPbPr RCA jacks. It also provides simultaneous downconversion of signals to 480i through composite and S-video jacks.
It has variable aspect ratio selection for downconversion. Outputs include analog stereo audio plus Dolby AC3 through an optical jack.
An IEEE-1394 FireWire jack was provided for connection to the PV-HD1000 D-VHS recorder/player.
The first models were mistakenly built with thw wrong ICs in them, and were very heat-sensitive. Panasonic will fix any TU-DST50Ws with this problem for free - it involves a chip upgrade to the correct Schottky ICs, which don't run as hot.
The problem manifests as blue streaking and speckles on the image. TU-DST50W tuners can be bought quite cheaply as demo units - I saw one a couple months back at a local Circuit City. The have been sold for as little as $500.
The TU-DST51 was an interim tuner to fix many of the problems with the 50. It also supports all native ATSC formats and outputs YPbPr. It does not do simultaneous downconversion to composite video (no S-video option), but this output can be selected via a rear-panel switch. Dolby AC-3 optical and the IEEE-1394 interface are once again included.
The TU-DST51 also has a second NTSC tuner for analong signals with its own composite output and stereo audio.
TU-DST51 tuners are also available used. I have sen them as cheap as $650, but more typically $800 - $900.
Both products are discontinued from the Panasonic product line.