My menus are a little different than yours, but I found your manual on-line. The instructions are found on page 37-39.
Assuming you don't have your manual with you, the Menu Item you are looking for is "Modulator Setup." I suspect it is Menu => Installation => Setup => Modulator Setup.
If it were me, I'd select a channel on UHF that is not being used nor the channel either side in use.
Say 60 is it. After selecting 60 and closing out the menu, go to the TV2 and tune it to 60. See if that helped. My further advice would be if that does not help, go back to your previous Ch 73 (Cable) and tune the TV2 back to 73... if it it used to work I wouldn't mess with it.
Your manuals are available on-line at
Dish Manuals
