I know this is a very old receiver, maybe someone still remembers something about it or is still using an HR10. Perhaps I should post this in the SD forum, if the moderators think it should be moved please feel free.
Since the H10 works fine for SD and has an ATSC tuner I had use for one so I recently reactivated it. It is plugged into a SDTV (in an office) set to 4:3 and "full" but the picture is still letterboxed on the Directv channels. On the ATSC channels the picture has the correct ratio.
When I hit the format button it cycles through 4:3 full, 4:3 zoom and 4:3 letterbox. The picture zooms as expected for 4:3 zoom, is letterboxed as expected for 4:3 letterbox, and but 4:3 full leaves the picture unchanged from 4:3 letterbox.
Any ideas? I probably shouldn't hold my breath for any H10 software updates to come through the stream, so if this is a bug that was fixed in a software update that came out after this receiver was taken offline (sometime in summer 2006) I may be SOL